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
golang/go#53743.

Reviewed By: dvyukov

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

Author: thanm

compiler-rt/lib/tsan/go/build.bat

@@ -59,5 +59,8 @@ gcc ^
   -DSANITIZER_DEBUG=0 ^
   -O3 ^
   -fomit-frame-pointer ^
-  -msse4.2 ^
+  -msse3 ^
   -std=c++14
+
+rem "-msse3" used above to ensure continued support of older
+rem cpus (for now), see https://github.com/golang/go/issues/53743.

compiler-rt/lib/tsan/go/buildgo.sh

@@ -59,7 +59,9 @@ if [ "`uname -a | grep Linux`" != "" ]; then
 		ARCHCFLAGS="-m64 -mcpu=power8 -fno-function-sections"
 	elif [ "`uname -a | grep x86_64`" != "" ]; then
 		SUFFIX="linux_amd64"
-		ARCHCFLAGS="-m64 -msse4.2"
+		# -msse3 used below to ensure continued support of older
+		# cpus for now, see https://github.com/golang/go/issues/53743.
+		ARCHCFLAGS="-m64 -msse3"
 		OSCFLAGS="$OSCFLAGS -ffreestanding -Wno-unused-const-variable -Wno-unknown-warning-option"
 	elif [ "`uname -a | grep aarch64`" != "" ]; then
 		SUFFIX="linux_arm64"