[base] Use thread safe localtime_r() instead of localtime().

src/base/platform/platform-solaris.cc

Index: src/base/platform/platform-solaris.cc
diff --git a/src/base/platform/platform-solaris.cc b/src/base/platform/platform-solaris.cc
index a2ce2c13f633c5fc3c7b8c3334aa91b5883a7bdd..1764978883a80615729d5b01d91c46916757297d 100644
--- a/src/base/platform/platform-solaris.cc
+++ b/src/base/platform/platform-solaris.cc
@@ -38,7 +38,8 @@ namespace base {
 const char* OS::LocalTimezone(double time, TimezoneCache* cache) {
   if (std::isnan(time)) return "";
   time_t tv = static_cast<time_t>(std::floor(time/msPerSecond));
-  struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
+  struct tm tm;
+  struct tm* t = localtime_r(&tv, &tm);
   if (NULL == t) return "";
   return tzname[0];  // The location of the timezone string on Solaris.
 }