libunwind unbuildable for wasmxx-wasi

[trcrsired]

tons of files are not properly guarded with macros and i do not know to compile it. I do not think it is working at all.

[trcrsired]

@aheejin

[asl]

According to the docs https://github.com/llvm/llvm-project/blob/main/libunwind/docs/index.rst libunwind does not support wasm. So this is expected.

[trcrsired]

According to the docs https://github.com/llvm/llvm-project/blob/main/libunwind/docs/index.rst libunwind does not support wasm. So this is expected.

I have submitted a PR79667 to fix it

#79667

Can you review it?