Enable co19 test suite on dart test scripts.

tools/testing/dart/test_runner.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #library("test_runner");
 
 #import("status_file_parser.dart");
 #import("test_progress.dart");
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
  */
 
 final int NO_TIMEOUT = 0;
 
 
 String getBuildDir(Map configuration) {
   var buildDir = '';
-  var os = configuration['os'];
-  if (os == 'linux') {
+  var system = configuration['system'];
+  if (system == 'linux') {
     buildDir = 'out/';
-  } else if (os == 'macos') {
+  } else if (system == 'macos') {
     buildDir = 'xcodebuild/';
   }
   buildDir += (configuration['mode'] == 'debug') ? 'Debug_' : 'Release_';
   buildDir += configuration['architecture'] + '/';
   return buildDir;
 }
 
 
 String getExecutableName(Map configuration) {
   switch (configuration['component']) {
@@ skipping 169 matching lines @@
       numProcesses++;
     }
   }
 
   runTest(TestCase test) {
     progress.testAdded();
     tests.add(test);
     tryRunTest();
   }
 }