[libcxxabi] Fix test_exception_address_alignment test for ARM

Check _LIBCXXABI_ARM_EHABI macro instead of libunwind version.

Fixes PR34182

Differential revision: https://reviews.llvm.org/D50170

git-svn-id: https://llvm.org/svn/llvm-project/libcxxabi/trunk@339865 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed