[clang] [clang][driver] Add \<executable\>/../include/c++/v1 to include path on Darwin (PR #70817)

[Louis Dionne via cfe-commits]

https://github.com/ldionne requested changes to this pull request.

I think this is generally reasonable but I'm requesting a few changes.

https://github.com/llvm/llvm-project/pull/70817