Suppress races on mktime

tools/valgrind/tsan/suppressions.txt

 ############################
 # Real races in Chromium
 {
   bug_23433
   ThreadSanitizer:Race
   fun:*logging*SetMinLogLevel*
 }
 
 {
   bug_24419
@@ skipping 450 matching lines @@
 }
 
 {
   fun:timegm
   ThreadSanitizer:Race
   ...
   fun:timegm
 }
 
 {
+  fun:mktime
+  ThreadSanitizer:Race
+  ...
+  fun:mktime
+}
+
+{
   Benign race in nss (PR_EnterMonitor)
   ThreadSanitizer:Race
   fun:PR_EnterMonitor
 }
 
 ############################
 # TSan false positives
 {
   tsanbug_62a
   ThreadSanitizer:Race
@@ skipping 15 matching lines @@
   fun:WebCore::DocumentLoader::~DocumentLoader*
   fun:WebKit::WebDataSourceImpl::~WebDataSourceImpl*
 }
 
 {
   bug_70085b
   ThreadSanitizer:Race
   fun:WebCore::SecurityOrigin::~SecurityOrigin*
   fun:WTF::ThreadSafe*<WebCore::SecurityOrigin>::deref*
 }