[libunwind] [libunwind] Fix libunwind library path for runtime test (PR #110777)

[via cfe-commits]

zeroomega wrote:

> This can be merged by whoever sees the CI green first.

There are 6 failing build so far but all due to the "runner received a shutdown signal", not actually a build/test failure? Should I do another rebase to trigger a rerun? Or we can just land it now?

https://github.com/llvm/llvm-project/pull/110777