The question is, how much of this can you actually build?

I had a hell of a time a few months ago trying to compile the Security framework from OS X 10.9.5 (I wanted to update the cipher suites!). It needs to link to a bunch of internal, closed Apple code.

I did eventually get something to compile, so there's that. But I had to pull in a bunch of reverse-engineered headers from the Darling project and similar efforts, and whatever it was that xCode finally spit out didn't seem to actually run.