[clang] [WinEH] Fix crash, object unwinding in the except block (PR #172287)

[via cfe-commits]

MuellerMP wrote:

> This case(new and delete object) I think we should probably fix the EH numbering algorithm, This does not conflict with This PR

I argued throughout this PR that "fixing this in EH numbering" is not optimal since mixing SEH with C++ unwinding is generally not allowed in MS C++ and only seems to be supported by Borland C++. In the latter case I do not know how unwinding is generated (e.g. which personality is chosen).

What i noticed though: even if we mark the dtor as virtual for the delete sample there is still a scope begin+end.
That is also true if we delete the delete call and just have the ctor present.
Since this is legal in MS C++ I guess one can argue that we should indeed respect that in the numbering algo.

https://github.com/llvm/llvm-project/pull/172287