(Be warned, these are currently rather rough.)

Build Rust with this patch: rust-lang/rust#67126

mkdir gcc cd gcc git clone --depth 50 -b rust https://github.com/sapir/gcc-rust/ gcc-src (cd gcc-src/gcc/rust/gcc-rust; cargo build)

mkdir gcc-build cd gcc-build ../gcc-src/configure --prefix=$(pwd)/../gcc-install --enable-languages=c,c++,rust --disable-multilib --disable-bootstrap make make install

cd .. gcc-install/bin/gcc whatever.rs -o whatever