[lldb-dap] Conditionally check UBSan stack trace on Darwin only (#178655)
non-darwin platforms may have incorrect stop information location
heuristics. Enable assertion once UBSan stopInfo heuristic is updated.
I hit this locally, I don't see it hitting any CI bot but should, Mostly
likely the CI linux bots may not have `compiler_rt` run time enabled.
see
https://github.com/llvm/llvm-project/pull/177964#discussion_r2732271531