tsan: enable -msse4 when compiling tests

Vector SSE accesses make compiler emit __tsan_[unaligned_]read/write16 callbacks.
Make it possible to test these.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D114591

GitOrigin-RevId: d841086ae62118408e4211685c3e2f5fff0021b5
1 file changed