[clang] Extend `retcon.once` coroutines lowering to optionally produce a normal result (PR #66333)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

Oh, I am wondering if we have misunderstandings. I am not asking the reason why we don't have the problem which is discussing in  the change of CoroFrame.cpp in return continuation ABI. I understand that fully. 

What make me curious is the motivation case of the PR. I mean what can be presented in retcon.once ABI after the PR which is impossible/hard before. And how do we handle that in retcon ABI.

Sorry for confusion.

https://github.com/llvm/llvm-project/pull/66333