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

[Nick Sarnie via cfe-commits]

sarnex wrote:

Sorry, I kind of got lost in the above discussion. Are additional changes required in Clang to parse builtins unsupported on the current target to make sure we don't break anything or is only changing the result of `__has_builtin` acceptable?

https://github.com/llvm/llvm-project/pull/121839