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

[Heejin Ahn via cfe-commits]

aheejin 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?

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