Investigate building libunwind with --enable-per-thread-cache

By default, libunwind uses a global cache, which potentially has some performance issues, due to needing to lock the cache frequently.

Possibly there is some performance gains with --enable-per-thread-cache. I could not find much discussion about potential perf improvements besides on this PR: https://github.com/libunwind/libunwind/pull/8

I would also note, I saw several past issues around per thread caching in my searches, which I did not investigate deep enough to determine if all issues were real and resolved, but its worth investigating in this ticket.