[clang] [CIR] Add support for coroutine allocation failure (PR #220466)

[Erich Keane via cfe-commits]

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@@ -0,0 +1,80 @@
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -fclangir -fno-clangir-call-conv-lowering -Wno-coroutine-missing-unhandled-exception -emit-cir %s -o %t.cir
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erichkeane wrote:

```suggestion
// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu -fclangir -Wno-coroutine-missing-unhandled-exception -emit-cir %s -o %t.cir
```

IS that necessary?  I think @adams381 has been putting a comment to help figure out when that is necessary and when he can remove it, so if you're going to use it, we need a similar comment.

https://github.com/llvm/llvm-project/pull/220466