When linking scudo standalone on armv7, it can't find symbols related to
unwinding (e.g. __aeabi_unwind_cpp_pr0). This is probably because it
is passing --unwindlib=none. This patch hacks around the issue by adding
COMPILER_RT_UNWINDER_LINK_LIBS if we're using the LLVM unwinder.
I don't know anything about scudo, so I'm not sure what the original
This is a release blocker.
See also https://github.com/llvm/llvm-project/issues/56900