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

[Liviu Ionescu via cfe-commits]

ilg-ul wrote:

Can someone review this patch?

Exactly the same strategy (check if the desired subfolder is below `InstalledDir`, and, if not, check again below `Dir`), so this patch is consistent with the rest of the code. 

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