fatal error: Cocoa/Cocoa.h: no such file or directory

I have searched the entire system directory for this header and cannot locate it.
I understand that it's a file generally included in the xcode tools.

I am trying to emulate system7 on a rpi that's built into an old mac classic case using this project: https://github.com/ekbann/rpi-basilisk2-sdl2-nox

I am just getting stuck on the cocoa.h part. Note: I did have to manually cp some other headers like SDL* stuff

Any ideas?