[clang] [clang][Driver][Darwin] Optionally use xcselect to find macOS SDK (PR #119670)

[Steven Wu via cfe-commits]

https://github.com/cachemeifyoucan commented:

The idea looks good.

Need to add test. You should add `CLANG_USE_XCSELECT` as a requirement and label all the tests properly (including those will break). Maybe you can also remove the hack for `CLANG_NO_XCSELECT` but I am neutral on that.


https://github.com/llvm/llvm-project/pull/119670