Rewrite cxa guard implementation. am: 867c4b05d5 am: 4b664e515a am: af99765d4c am: e1d2b5ba8f

Original change: https://android-review.googlesource.com/c/platform/external/libcxxabi/+/1727435

Change-Id: If2f75718082e3f1592cb381097d2b88c6adcede0