In preperation of using d8 for running tests: Don't run d8-os when running with --isolates.

tools/test.py

 #!/usr/bin/env python
 #
 # Copyright 2008 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 1424 matching lines @@
   all_unused = [ ]
   unclassified_tests = [ ]
   globally_unused_rules = None
   for path in paths:
     for mode in options.mode:
       env = {
         'mode': mode,
         'system': utils.GuessOS(),
         'arch': options.arch,
         'simulator': options.simulator,
-        'crankshaft': options.crankshaft
+        'crankshaft': options.crankshaft,
+        'isolates': options.isolates
       }
       test_list = root.ListTests([], path, context, mode, [])
       unclassified_tests += test_list
       (cases, unused_rules, all_outcomes) = config.ClassifyTests(test_list, env)
       if globally_unused_rules is None:
         globally_unused_rules = set(unused_rules)
       else:
         globally_unused_rules = globally_unused_rules.intersection(unused_rules)
       all_cases += ShardTests(cases, options)
       all_unused.append(unused_rules)
@@ skipping 50 matching lines @@
     for entry in timed_tests[:20]:
       t = FormatTime(entry.duration)
       sys.stderr.write("%4i (%s) %s\n" % (index, t, entry.GetLabel()))
       index += 1
 
   return result
 
 
 if __name__ == '__main__':
   sys.exit(Main())