[presubmit] Enable runtime/threadsafe_fn linter checking.

src/base/platform/platform-posix.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Platform-specific code for POSIX goes here. This is not a platform on its
 // own, but contains the parts which are the same across the POSIX platforms
 // Linux, MacOS, FreeBSD, OpenBSD, NetBSD and QNX.
 
 #include <errno.h>
 #include <limits.h>
@@ skipping 366 matching lines @@
 
 
 void OS::ClearTimezoneCache(TimezoneCache* cache) {
   DCHECK(cache == NULL);
 }
 
 
 double OS::DaylightSavingsOffset(double time, TimezoneCache*) {
   if (std::isnan(time)) return std::numeric_limits<double>::quiet_NaN();
   time_t tv = static_cast<time_t>(std::floor(time/msPerSecond));
-  struct tm* t = localtime(&tv);
+  struct tm* t = localtime(&tv);  // NOLINT(runtime/threadsafe_fn)
   if (NULL == t) return std::numeric_limits<double>::quiet_NaN();
   return t->tm_isdst > 0 ? 3600 * msPerSecond : 0;
 }
 
 
 int OS::GetLastError() {
   return errno;
 }
 
 
@@ skipping 350 matching lines @@
 
 void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
   pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
   int result = pthread_setspecific(pthread_key, value);
   DCHECK_EQ(0, result);
   USE(result);
 }
 
 }  // namespace base
 }  // namespace v8