[clang] [clang][CodeGen] Emit coro.dead intrinsic to improve coroutine allocation elision (PR #190295)

[Andrew Lazarev via cfe-commits]

alazarev wrote:

Looks like it broke https://lab.llvm.org/buildbot/#/builders/55/builds/26258

https://github.com/llvm/llvm-project/pull/190295