[clang] [libunwind] [libunwind][WebAssembly] Make libunwind compilable (PR #92192)

[Derek Schuff via cfe-commits]

https://github.com/dschuff approved this pull request.

These changes make sense from the wasm point of view, and it looks like you've address the comment, so LGTM

https://github.com/llvm/llvm-project/pull/92192