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

src/base/platform/platform-linux.cc

Index: src/base/platform/platform-linux.cc
diff --git a/src/base/platform/platform-linux.cc b/src/base/platform/platform-linux.cc
index f00acf1892c50029b28a6e20a33a80e3f8e2e090..e0541c5d03214badcd51c869845485416e52d368 100644
--- a/src/base/platform/platform-linux.cc
+++ b/src/base/platform/platform-linux.cc
@@ -108,7 +108,8 @@ const char* OS::LocalTimezone(double time, TimezoneCache* cache) {
 #else
   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 (!t || !t->tm_zone) return "";
   return t->tm_zone;
 #endif
@@ -121,7 +122,8 @@ double OS::LocalTimeOffset(TimezoneCache* cache) {
   return 0;
 #else
   time_t tv = time(NULL);
-  struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
+  struct tm tm;
+  struct tm* t = localtime_r(&tv, &tm);
   // tm_gmtoff includes any daylight savings offset, so subtract it.
   return static_cast<double>(t->tm_gmtoff * msPerSecond -
                              (t->tm_isdst > 0 ? 3600 * msPerSecond : 0));