I tried compiling the latest master on MacOS Mojave. Some new libs were downloaded like Python 3.9. Just to make sure, I removed entirely libs and build folders and let make update then make do their job. I still get this error:
Undefined symbols for architecture x86_64:
"___isPlatformVersionAtLeast", referenced from:
_py_posix_spawn in libpython3.9.a(posixmodule.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [bin/Blender.app/Contents/MacOS/Blender] Error 1
make[2]: *** [source/creator/CMakeFiles/blender.dir/all] Error 2
make[1]: *** [all] Error 2
make: *** [all] Error 2