[test] Restrict msan to default variant.

tools/run-tests.py

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 336 matching lines @@
   options.command_prefix = shlex.split(options.command_prefix)
   options.extra_flags = shlex.split(options.extra_flags)
 
   if options.gc_stress:
     options.extra_flags += GC_STRESS_FLAGS
 
   if options.asan:
     options.extra_flags.append("--invoke-weak-callbacks")
     options.extra_flags.append("--omit-quit")
 
+  if options.msan:
+    VARIANTS = ["default"]
+
   if options.tsan:
     VARIANTS = ["default"]
     suppressions_file = os.path.join(os.path.dirname(os.path.abspath(__file__)),
                                      'sanitizers', 'tsan_suppressions.txt')
     tsan_options = '%s suppressions=%s' % (
         os.environ.get('TSAN_OPTIONS', ''), suppressions_file)
     os.environ['TSAN_OPTIONS'] = tsan_options
 
   if options.j == 0:
     options.j = multiprocessing.cpu_count()
@@ skipping 271 matching lines @@
   exit_code = runner.Run(options.j)
   overall_duration = time.time() - start_time
 
   if options.time:
     verbose.PrintTestDurations(suites, overall_duration)
   return exit_code
 
 
 if __name__ == "__main__":
   sys.exit(Main())