[compiler-rt] [libunwind] [llvm] [WebAssembly] Move __cpp_exception to libunwind (PR #185770)

[Alex Crichton via cfe-commits]

alexcrichton wrote:

Agreed yeah, I suspect that longjmp/setjmp in wasi-libc are probably broken since the change awhile back to avoid adding a weak definition of `__c_longjmp` to all objects. The main motivation of this PR was fixing wasi-sdk with LLVM 22 and since I needed to add the symbol to libunwind I figured I'd go ahead and move it. I'll test out what's needed for setjmp/longjmp in wasi-libc and I'll report back here with a follow-up to probably just delete the symbol in compiler-rt.

https://github.com/llvm/llvm-project/pull/185770