libunwind is out of sync with other libraries we pull from llvm

[sbc100]

According to system/lib/libunwind/readme.txt we are on version 8.0.0 where as compiler-rt, libc++, and libc++abi are all on 10.0.0.

[sbc100]

I noticed this because if out libunwind code doesn't compile if clang's builtin unwind.h (which is tip of tree) gets picked up (while working on #13090). I'm not sure updating to 10.0.0 would solve this issue but its worth a try.

[sbc100]

@aheejin any reason this might not be a simple process?

[aheejin]

I don't think so. We use libunwind mostly for its headers and our own stub (Unwind-wasm.cpp), so I think we can mostly just use the 10.0.0 release as is and I can't think of any possible issues at the moment.

[sbc100]

Do you fancy doing and upgrade? (no pressure I can do it if you don't have time).

[aheejin]

Done in #13098 (By the way I updated it to 11.0.0).