Revert "[Driver] Properly report error for unsupported powerpc darwin/macos triples"

This reverts commit 9f77facf.

The change unintentionally changed lots of codegen, see
https://github.com/llvm/llvm-project/issues/47698#issuecomment-1714548640

Also revert a follow-up:
This reverts commit b40a5bea.