[compiler-rt] [libunwind] [llvm] Fix compiling/using libunwind for wasm targets (PR #185770)

[Alex Crichton via cfe-commits]

alexcrichton wrote:

@sbc100 would you be up for reviewing this?

also, while I've got you here, are there any blockers to merging #168449 with it being approved now?

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