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

[Joseph Huber via cfe-commits]

jhuber6 wrote:

> `CodeGenHipStdPar/unsupported-builtins.cpp` is pretty interesting actually, it looks like it tests for some behavior in CodeGen that seems like it's trying to fix the exact same problem
> 
> The other two tests seem to be actually unrelated breakages though.

Maybe @AlexVlx would know about this in general, but I'd definitely say it's problematic behavior.

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