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

[Steven Wu via cfe-commits]

https://github.com/cachemeifyoucan commented:

Let's investigate to see all those test failed (many of them have versioned deployment target).

Maybe it is because the `darwin` legacy OS in the triple? Maybe don't use `xcselect` when it is darwin since the modern spelling should `macOS` family?

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