[clang] [clang][CodeGen] Trigger AST lookup for libfunction builtins (PR #209997)

[Chuanqi Xu via cfe-commits]

https://github.com/ChuanqiXu9 commented:

The patch looks better. But if possible, we really hope we can understand the underlying reasons so that we can make the software better.

https://github.com/llvm/llvm-project/pull/209997