[clang] Revert "[Clang] __has_builtin should return false for aux triple builtins (#121839) (PR #124626)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

Sad.... I saw the other thing, I'm not sure how we can manage that without a new builtin just so CUDA can do what they need here.

https://github.com/llvm/llvm-project/pull/124626