Have make suppress error messages for the .o including it. You can have another file implement any missing symbols with a weak attribute so the linker will not

Have make suppress error messages for the .o including it. You can have another file implement any missing symbols with a weak attribute so the linker will not complain if your evil object file fails to be built. If you go with C++ then you have an entire Turing complete language executed at compile time to do whatever nasty thing your heart desires. I agree there are much easier alternatives... but it's an intellectually interesting attack vector.