If wayland-client is not in the default lib folder or include folder, ie. instead of /usr/include/wayland-client.h it is /usr/include/wayland/wayland-client.h, dwlmsg compilation will fail. Dwlmsg should use pkg-config to find wayland-client.pc file and obtain the libs and include flags. For example, opensuse keeps wayland-client.h under /usr/include/wayland.
If wayland-client is not in the default lib folder or include folder, ie. instead of /usr/include/wayland-client.h it is /usr/include/wayland/wayland-client.h, dwlmsg compilation will fail. Dwlmsg should use pkg-config to find wayland-client.pc file and obtain the libs and include flags. For example, opensuse keeps wayland-client.h under /usr/include/wayland.