[clang] [llvm] [PowerPC] Add target feature validation for builtins in Sema (PR #187371)

[Lei Huang via cfe-commits]

lei137 wrote:

> It seems there are no tests that specifically trigger and verify the new `needs target feature` Sema error for PPC builtins.

Yes, that is true.  I didn't think to add any as all the test case updates in this PR are related to the earlier trigger.  New feature bits were set so that the test cases can by-pass this trigger to proceed to what it was originally trying to test.

This is the implementation patch so I can add Sema tests to address your review comment: https://github.com/llvm/llvm-project/pull/184681#pullrequestreview-3955235809.

https://github.com/llvm/llvm-project/pull/187371