[clang] [Clang] Reland '__has_builtin should return false for aux triple builtins' (PR #126324)

[Nick Sarnie via cfe-commits]

sarnex wrote:

> This seems to have been undone.


Yeah just noticed the same thing, looks like that feedback was only in this PR, my bad. Fixed now.

https://github.com/llvm/llvm-project/pull/126324