[libunwind] [libunwind] Fix execution flow imbalance when using C++ Exceptions (PR #165066)

[Med Ismail Bennani via cfe-commits]

medismailben wrote:

> Can you add a test like we discussed? It might have to be in LLDB but that's already better than nothing.

I can try adding an lldb test but I need to make sure we can `DYLD_INSERT_LIBRARY` the built `libunwind.dylib` first.

https://github.com/llvm/llvm-project/pull/165066