I can't disagree with you as tools for managing builds, but isn't clang a pretty good C compiler which does everything you need and works pretty much everywhere?
Yup, but I'd like to remove the Objective-C{,++} support I'm almost definitely not gonna use in the foreseeable future, for example.
Take it as my obsession for minimalism.
Since Objective-C is so similar to C, I don't see why you would write a compiler for one and not do the amount of work to get it working with C and not do the comparatively smaller amount to get Objective-C to work.