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

[Louis Dionne via cfe-commits]

ldionne 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?

Merged since we have basically all green now. FYI, the "shutdown signal" thing is that our CI workers are running on preemptable VMs. So they sometimes get killed (shutdown signal) and we have another GH Action that restarts them. It's a bit funky but it saves a lot of cost for the fleet.

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