[clang] [Clang][CodeGen][Coroutines] Make coroutine startup exception-safe (C… (PR #202279)

[Yexuan Xiao via cfe-commits]

YexuanXiao wrote:

@ChuanqiXu9 Can you take a look at this PR? I found a new way to avoid the HALO failure issue I caused back in February.

https://github.com/llvm/llvm-project/pull/202279