tsan: update Go x86 build rules to back off to sse3

This is a partial revert of https://reviews.llvm.org/D106948, changing
just the Go build rules to remove -msse4.2 and revert back to -msse3,
so as to preserve support for older x86 machines. More details at
https://github.com/golang/go/issues/53743.

Reviewed By: dvyukov

Differential Revision: https://reviews.llvm.org/D129482