Esp8266: Linux - fatal: No names found and undefined reference to `app_entry_custom()'

Question

as Gentoo user I build everything from sources, but I have problem with building toolchain for esp8266. I came up with this script:

#!/bin/sh
# note: eselect python2 before, because of gcc
# prepare board
mkdir -p ~/Arduino/hardware/esp8266com
cd ~/Arduino/hardware/esp8266com
git clone --recursive --depth 1 https://github.com/esp8266/Arduino.git esp8266
# use system python3
mkdir esp8266/tools/python3
ln -s /usr/bin/python3 esp8266/tools/python3/python3
# build toolchain
cd ~/Arduino
git clone --recursive --depth 1 https://github.com/pfalcon/esp-open-sdk.git
cd esp-open-sdk
sed -i "193s/.*/ |\$EGREP '^GNU bash, version (3\\.[1-9]|4|5)')/" crosstool-NG/configure.ac # add bash5 support
echo CT_DEBUG_gdb=n >> crosstool-config-overrides # don't build gdb
make STANDALONE=n
# "install" esp-open-sdk
ln -sf ~/Arduino/esp-open-sdk/xtensa-lx106-elf ~/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf

It builded successfully, but I get errors during building project:

(...)
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/python3/python3 /home/urhen/Arduino/hardware/esp8266com/esp8266/tools/makecorever.py --build_path /tmp/arduino_build_179995 --platform_path /home/urhen/Arduino/hardware/esp8266com/esp8266 --version unix-2.7.0-dev
fatal: No names found, cannot describe anything.
(...)
Linking everything together...
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-gcc -CC -E -P -DVTABLES_IN_FLASH /home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/ld/eagle.app.v6.common.ld.h -o /tmp/arduino_build_179995/local.eagle.app.v6.common.ld
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-gcc -fno-exceptions -Wl,-Map -Wl,/tmp/arduino_build_179995/sketch_apr19a.ino.map -g -Wall -Wextra -Os -nostdlib -Wl,--no-check-sections -u app_entry -u _printf_float -u _scanf_float -Wl,-static -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lib -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lib/NONOSDK22x_190703 -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/ld -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/libc/xtensa-lx106-elf/lib -Teagle.flash.4m2m.ld -Wl,--gc-sections -Wl,-wrap,system_restart_local -Wl,-wrap,spi_flash_read -o /tmp/arduino_build_179995/sketch_apr19a.ino.elf -Wl,--start-group /tmp/arduino_build_179995/sketch/sketch_apr19a.ino.cpp.o /tmp/arduino_build_179995/core/core.a -lhal -lphy -lpp -lnet80211 -llwip2-536-feat -lwpa -lcrypto -lmain -lwps -lbearssl -laxtls -lespnow -lsmartconfig -lairkiss -lwpa2 -lstdc++ -lm -lc -lgcc -Wl,--end-group -L/tmp/arduino_build_179995
/tmp/arduino_build_179995/core/core.a(core_esp8266_main.cpp.o):(.text.app_entry+0x0): undefined reference to `app_entry_custom()'
/tmp/arduino_build_179995/core/core.a(core_esp8266_main.cpp.o): In function `app_entry':
/home/urhen/Arduino/hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_main.cpp:318: undefined reference to `app_entry_custom()'
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board LOLIN(WEMOS) D1 R2 & mini.

What am I missing?

Log:

/usr/share/arduino/arduino-builder -dump-prefs -logger=machine -hardware /usr/share/arduino/hardware -hardware /home/urhen/Arduino/hardware -tools /usr/share/arduino/hardware/tools/avr -libraries /home/urhen/Arduino/libraries -fqbn=esp8266com:esp8266:d1_mini:xtal=80,vt=flash,exception=legacy,ssl=all,eesz=4M2M,ip=lm2f,dbg=Disabled,lvl=None____,wipe=none,baud=921600 -ide-version=10807 -build-path /tmp/arduino_build_418955 -warnings=all -prefs=build.warn_data_percentage=75 -verbose /tmp/untitled878766377.tmp/sketch_apr19a/sketch_apr19a.ino
/usr/share/arduino/arduino-builder -compile -logger=machine -hardware /usr/share/arduino/hardware -hardware /home/urhen/Arduino/hardware -tools /usr/share/arduino/hardware/tools/avr -libraries /home/urhen/Arduino/libraries -fqbn=esp8266com:esp8266:d1_mini:xtal=80,vt=flash,exception=legacy,ssl=all,eesz=4M2M,ip=lm2f,dbg=Disabled,lvl=None____,wipe=none,baud=921600 -ide-version=10807 -build-path /tmp/arduino_build_418955 -warnings=all -prefs=build.warn_data_percentage=75 -verbose /tmp/untitled878766377.tmp/sketch_apr19a/sketch_apr19a.ino
Using board 'd1_mini' from platform in folder: /home/urhen/Arduino/hardware/esp8266com/esp8266
Using core 'esp8266' from platform in folder: /home/urhen/Arduino/hardware/esp8266com/esp8266
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/python3/python3 /home/urhen/Arduino/hardware/esp8266com/esp8266/tools/makecorever.py --build_path /tmp/arduino_build_418955 --platform_path /home/urhen/Arduino/hardware/esp8266com/esp8266 --version unix-2.7.0-dev
Detecting libraries used...
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-g++ -D__ets__ -DICACHE_FLASH -U__STRICT_ANSI__ -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lwip2/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/libc/xtensa-lx106-elf/include -I/tmp/arduino_build_418955/core -c -w -Os -g -mlongcalls -mtext-section-literals -fno-rtti -falign-functions=4 -std=gnu++11 -ffunction-sections -fdata-sections -fno-exceptions -w -x c++ -E -CC -DNONOSDK22x_190703=1 -DF_CPU=80000000L -DLWIP_OPEN_SRC -DTCP_MSS=536 -DLWIP_FEATURES=1 -DLWIP_IPV6=0 -DARDUINO=10807 -DARDUINO_ESP8266_WEMOS_D1MINI -DARDUINO_ARCH_ESP8266 "-DARDUINO_BOARD=\"ESP8266_WEMOS_D1MINI\"" -DFLASHMODE_DIO -DESP8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/cores/esp8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/variants/d1_mini /tmp/arduino_build_418955/sketch/sketch_apr19a.ino.cpp -o /dev/null
Generating function prototypes...
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-g++ -D__ets__ -DICACHE_FLASH -U__STRICT_ANSI__ -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lwip2/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/libc/xtensa-lx106-elf/include -I/tmp/arduino_build_418955/core -c -w -Os -g -mlongcalls -mtext-section-literals -fno-rtti -falign-functions=4 -std=gnu++11 -ffunction-sections -fdata-sections -fno-exceptions -w -x c++ -E -CC -DNONOSDK22x_190703=1 -DF_CPU=80000000L -DLWIP_OPEN_SRC -DTCP_MSS=536 -DLWIP_FEATURES=1 -DLWIP_IPV6=0 -DARDUINO=10807 -DARDUINO_ESP8266_WEMOS_D1MINI -DARDUINO_ARCH_ESP8266 "-DARDUINO_BOARD=\"ESP8266_WEMOS_D1MINI\"" -DFLASHMODE_DIO -DESP8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/cores/esp8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/variants/d1_mini /tmp/arduino_build_418955/sketch/sketch_apr19a.ino.cpp -o /tmp/arduino_build_418955/preproc/ctags_target_for_gcc_minus_e.cpp
/usr/bin/arduino-ctags -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives /tmp/arduino_build_418955/preproc/ctags_target_for_gcc_minus_e.cpp
Compiling sketch...
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/python3/python3 /home/urhen/Arduino/hardware/esp8266com/esp8266/tools/signing.py --mode header --publickey /tmp/untitled878766377.tmp/sketch_apr19a/public.key --out /tmp/arduino_build_418955/core/Updater_Signing.h
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-g++ -D__ets__ -DICACHE_FLASH -U__STRICT_ANSI__ -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lwip2/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/libc/xtensa-lx106-elf/include -I/tmp/arduino_build_418955/core -c -Wall -Wextra -Os -g -mlongcalls -mtext-section-literals -fno-rtti -falign-functions=4 -std=gnu++11 -MMD -ffunction-sections -fdata-sections -fno-exceptions -DNONOSDK22x_190703=1 -DF_CPU=80000000L -DLWIP_OPEN_SRC -DTCP_MSS=536 -DLWIP_FEATURES=1 -DLWIP_IPV6=0 -DARDUINO=10807 -DARDUINO_ESP8266_WEMOS_D1MINI -DARDUINO_ARCH_ESP8266 "-DARDUINO_BOARD=\"ESP8266_WEMOS_D1MINI\"" -DFLASHMODE_DIO -DESP8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/cores/esp8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/variants/d1_mini /tmp/arduino_build_418955/sketch/sketch_apr19a.ino.cpp -o /tmp/arduino_build_418955/sketch/sketch_apr19a.ino.cpp.o
Compiling libraries...
Compiling core...
Using previously compiled file: /tmp/arduino_build_418955/core/cont.S.o
Using previously compiled file: /tmp/arduino_build_418955/core/umm_malloc/umm_info.c.o
Using previously compiled file: /tmp/arduino_build_418955/core/umm_malloc/umm_integrity.c.o
Using previously compiled file: /tmp/arduino_build_418955/core/umm_malloc/umm_local.c.o
Using previously compiled file: /tmp/arduino_build_418955/core/umm_malloc/umm_poison.c.o
Using previously compiled file: /tmp/arduino_build_418955/core/Esp-frag.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/core_esp8266_postmortem.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/WMath.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/heap.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/core_esp8266_sigma_delta.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/WString.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/libc_replacements.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/core_esp8266_si2c.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/gdb_hooks.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/core_esp8266_timer.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/spiffs_api.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/Stream.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/abi.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/Esp.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/Esp-version.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-g++ -D__ets__ -DICACHE_FLASH -U__STRICT_ANSI__ -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lwip2/include -I/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/libc/xtensa-lx106-elf/include -I/tmp/arduino_build_418955/core -c -Wall -Wextra -Os -g -mlongcalls -mtext-section-literals -fno-rtti -falign-functions=4 -std=gnu++11 -MMD -ffunction-sections -fdata-sections -fno-exceptions -DNONOSDK22x_190703=1 -DF_CPU=80000000L -DLWIP_OPEN_SRC -DTCP_MSS=536 -DLWIP_FEATURES=1 -DLWIP_IPV6=0 -DARDUINO=10807 -DARDUINO_ESP8266_WEMOS_D1MINI -DARDUINO_ARCH_ESP8266 "-DARDUINO_BOARD=\"ESP8266_WEMOS_D1MINI\"" -DFLASHMODE_DIO -DESP8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/cores/esp8266 -I/home/urhen/Arduino/hardware/esp8266com/esp8266/variants/d1_mini /home/urhen/Arduino/hardware/esp8266com/esp8266/cores/esp8266/Updater.cpp -o /tmp/arduino_build_418955/core/Updater.cpp.o
Using previously compiled file: /tmp/arduino_build_418955/core/core_esp8266_spi_utils.cpp.o
[cut due to characters limit]
Using previously compiled file: /tmp/arduino_build_418955/core/Schedule.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Esp-frag.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Esp-version.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Esp.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/FS.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/FSnoop.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/FunctionalInterrupt.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/HardwareSerial.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/IPAddress.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/MD5Builder.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Print.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Schedule.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/StackThunk.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Stream.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/StreamString.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Tone.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/Updater.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/WMath.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/WString.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/abi.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/base64.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/cbuf.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/cont.S.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/cont_util.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_app_entry_noextra4k.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_eboot_command.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_features.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_flash_utils.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_i2s.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_main.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_noniso.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_phy.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_postmortem.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_si2c.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_sigma_delta.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_spi_utils.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_timer.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_waveform.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_wiring.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_wiring_analog.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_wiring_digital.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_wiring_pulse.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_wiring_pwm.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/core_esp8266_wiring_shift.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/crc32.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/debug.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/flash_hal.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/gdb_hooks.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/heap.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/libb64/cdecode.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/libb64/cencode.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/libc_replacements.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/sntp-lwip2.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/spiffs/spiffs_cache.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/spiffs/spiffs_check.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/spiffs/spiffs_gc.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/spiffs/spiffs_hydrogen.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/spiffs/spiffs_nucleus.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/spiffs_api.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/sqrt32.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/time.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/uart.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/umm_malloc/umm_info.c.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/umm_malloc/umm_integrity.c.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/umm_malloc/umm_local.c.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/umm_malloc/umm_malloc.cpp.o
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-ar cru /tmp/arduino_build_418955/core/core.a /tmp/arduino_build_418955/core/umm_malloc/umm_poison.c.o
Linking everything together...
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-gcc -CC -E -P -DVTABLES_IN_FLASH /home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/ld/eagle.app.v6.common.ld.h -o /tmp/arduino_build_418955/local.eagle.app.v6.common.ld
/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/xtensa-lx106-elf/bin/xtensa-lx106-elf-gcc -fno-exceptions -Wl,-Map -Wl,/tmp/arduino_build_418955/sketch_apr19a.ino.map -g -Wall -Wextra -Os -nostdlib -Wl,--no-check-sections -u app_entry -u _printf_float -u _scanf_float -Wl,-static -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lib -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/lib/NONOSDK22x_190703 -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/ld -L/home/urhen/Arduino/hardware/esp8266com/esp8266/tools/sdk/libc/xtensa-lx106-elf/lib -Teagle.flash.4m2m.ld -Wl,--gc-sections -Wl,-wrap,system_restart_local -Wl,-wrap,spi_flash_read -o /tmp/arduino_build_418955/sketch_apr19a.ino.elf -Wl,--start-group /tmp/arduino_build_418955/sketch/sketch_apr19a.ino.cpp.o /tmp/arduino_build_418955/core/core.a -lhal -lphy -lpp -lnet80211 -llwip2-536-feat -lwpa -lcrypto -lmain -lwps -lbearssl -laxtls -lespnow -lsmartconfig -lairkiss -lwpa2 -lstdc++ -lm -lc -lgcc -Wl,--end-group -L/tmp/arduino_build_418955
/tmp/arduino_build_418955/core/core.a(core_esp8266_main.cpp.o):(.text.app_entry+0x0): undefined reference to `app_entry_custom()'
/tmp/arduino_build_418955/core/core.a(core_esp8266_main.cpp.o): In function `app_entry':
/home/urhen/Arduino/hardware/esp8266com/esp8266/cores/esp8266/core_esp8266_main.cpp:318: undefined reference to `app_entry_custom()'
collect2: error: ld returned 1 exit status
exit status 1
Error compiling for board LOLIN(WEMOS) D1 R2 & mini.

Answer 1

You did a shallow copy of the git repo:
The solution is to ensure that the initial clone of the repo in the build environment was not a shallow clone (i.e. the git clone command was not used with --depth, --shallow-since or --shallow-exclude parameters). so change your

git clone --recursive --depth 1 https://github.com/esp8266/Arduino.git esp8266
....
git clone --recursive --depth 1 https://github.com/pfalcon/esp-open-sdk.git

to

git clone --recursive https://github.com/esp8266/Arduino.git esp8266
.... 
git clone --recursive https://github.com/pfalcon/esp-open-sdk.git

and make sure your *.ino contains at least

 setup(){}

AND

loop(){}

• urhen: This fixed "fatal: No names found, cannot describe anything.", but there are still "undefined reference to `app_entry_custom()'".
• Codebreaker007: Can you now ADD the current error message to your question (edit it) - because error message have to be worked top down not bottom up -btw whats in the sketch apr*.ino? Are you using docker images?
• urhen: apr*.ino is empty setup() and main(), I don't use docker.
• Codebreaker007: See my edit in the answer
• urhen: My *.ino is fine, this linker error mean that I lacking some shared object (I'm not sure if I can call it that in this case), but I have no clue which file it need and how to add it.