[clang] [Clang][ExprConstant] Normalize aux target builtin IDs before dispatch (PR #201805)

[Timm Baeder via cfe-commits]

tbaederr wrote:

I don't know anything about auxiliary builtin IDs, what they are or why they exist.
BUT:
 1) If this is so important, shouldn't `getConstantEvaluatedBuiltinID` be a member function of `CallExpr`?
 2) `CallExpr::getBuiltinID()` is already very slow, so adding another layer do that seems bad.

https://github.com/llvm/llvm-project/pull/201805