Patch re2 to support MSan.

third_party/re2/util/util.h

Index: third_party/re2/util/util.h
diff --git a/third_party/re2/util/util.h b/third_party/re2/util/util.h
index de1ef5b24f4ea1314fee4be077932fc3be93d3e5..49159c2e446768c75ba6f43599491a999e58f026 100644
--- a/third_party/re2/util/util.h
+++ b/third_party/re2/util/util.h
@@ -129,6 +129,14 @@ static inline uint64 Hash64StringWithSeed(const char* s, int len, uint32 seed) {
   return ((uint64)x << 32) | y;
 }
 
+inline bool RunningOnValgrindOrMemorySanitizer() {
+#if defined(MEMORY_SANITIZER)
+  return true;
+#else
+  return RunningOnValgrind();
+#endif
+}
+
 }  // namespace re2
 
 #include "util/arena.h"