[libunwind] [libunwind][WebAssembly] Don't build libunwind.cpp (PR #73196)

[Alexander Richardson via cfe-commits]

arichardson wrote:

> > The commit message is slightly misleading, it appears there are some parts of the file that are actually used?
> 
> As the commit message says, we only use https://github.com/llvm/llvm-project/blob/main/libunwind/src/Unwind-wasm.c and not libunwind.cpp. We don't use any parts of libunwind.cpp. Do you have any suggestions on how to improve the message to make it clearer?

Looking at the file, there is some code that will still be compiled for wasm (at least for debug builds). If those functions are also not used for wasm they should be ifdef'd out as well?

Commit message could be something like `Omit unused parts of libunwind.cpp for WASM`. 



https://github.com/llvm/llvm-project/pull/73196