[llvm] [Coroutines] Implement elision for noop coroutines (PR #174353)

[Chuanqi Xu via llvm-commits]

ChuanqiXu9 wrote:

>  It seems clang forgot to add function attributes to await_suspend wrappers. The inliner refuses to inline callees into await_suspend because their attributes mismatch.

Sounds like an important issue to me.

https://github.com/llvm/llvm-project/pull/174353