[tsan] Add environment variable TSAN_SYMBOLIZER_PATH as we do in other sanitizers

[Enna1]

Summary

ASan, LSan, MSan and UBSan all allow to use environment variable *SAN_SYMBOLIZER_PATH to pass the symbolizer path, this patch add TSAN_SYMBOLIZER_PATH to TSan.

compiler-rt/lib/tsan/rtl/tsan_flags.cpp

 }
 
 void InitializeFlags(Flags *f, const char *env, const char *env_option_name) {
   SetCommonFlagsDefaults();
   {
     // Override some common flags defaults.
     CommonFlags cf;
     cf.CopyFrom(*common_flags());
+    cf.external_symbolizer_path = GetEnv("TSAN_SYMBOLIZER_PATH");
     cf.allow_addr2line = true;
     if (SANITIZER_GO) {
       // Does not work as expected for Go: runtime handles SIGABRT and crashes.
       cf.abort_on_error = false;
       // Go does not have mutexes.
       cf.detect_deadlocks = false;
     }
     cf.print_suppressions = false;