[clang] [llvm] [ARM] Add support for Windows SEH (PR #184953)

[Martin Storsjö via cfe-commits]

mstorsjo wrote:

https://github.com/llvm/llvm-project/pull/187860 caused these warnings; it seems like https://github.com/llvm/llvm-project/pull/198286 which is merged now should sort this out. So if you rebase past a version with that fix included, it should hopefully pass now.

https://github.com/llvm/llvm-project/pull/184953