I wrote up a PDF for the Rigging Dojo C++ API course for how to set up XCode to work with Maya. I was the only person in the class using XCode, so I had to figure everything out by myself. I figured I would write up something to help anyone who came after me.
Update: I've since moved on from XCode for Maya, I'm using CLion now. I like the CMake/Clang system a lot more and might one day do a write up on getting it set up. For now, it's probably best to just consult Chad Vernon's CMake Playlist
Or go to my Github and check out one of the C++ repos for a more updated CMake file