Use test.dart for dartc buildbot. Ensure that test.dart creates the build directory.

tools/testing/dart/test_suite.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_suite");
 
 #import("status_file_parser.dart");
 #import("test_runner.dart");
 #import("multitest.dart");
 
@@ skipping 453 matching lines @@
                 browserFlag = 'safari';
                 break;
             }
           }
         }
         args = ['--out', htmlPath, '--browser', browserFlag];
         
       } else {
         args = ['--no-timeout'];
         if (component == 'dartium') {
-          var dartFlags = ['--enable_asserts', '--enable_type_checks'];
+          var dartFlags = ['--enable_asserts',
+                           '--enable_type_checks',
+                           '--ignore-unrecognized-flags'];
           dartFlags.addAll(vmOptions);
           args.add('--dart-flags=${Strings.join(dartFlags, " ")}');
         }
         args.add(htmlPath);
       }
       // Create BrowserTestCase and queue it.
       var testCase = new BrowserTestCase(
           testName,
           compilerExecutable,
           compilerArgs,
@@ skipping 20 matching lines @@
     testUniqueName = testUniqueName.replaceAll('/', '_');
     // Create '[build dir]/generated_tests/$component/$testUniqueName',
       // including any intermediate directories that don't exist.
     var generatedTestPath = ['generated_tests',
                              configuration['component'],
                              testUniqueName];
 
     String tempDirPath = TestUtils.buildDir(configuration);
     Directory tempDir = new Directory(tempDirPath);
     if (!tempDir.existsSync()) {
-      throw new Exception('Build directory $tempDirPath does not exist.');
+      // Dartium tests can be run with no build step, with no output directory.
+      // This special case builds the build directory that should be there.
+      var buildPath = tempDirPath.split('/');
+      tempDirPath = buildPath[0];
+      if (tempDirPath == '') {
+        throw new Exception(
+            'Non-relative path to build directory in test_suite.dart');
+      }
+      buildPath.removeRange(0, 1);
+      if (buildPath.last() == '') buildPath.removeLast();
+      buildPath.addAll(generatedTestPath);
+      generatedTestPath = buildPath;
+      tempDir = new Directory(tempDirPath);
+      if (!tempDir.existsSync()) {
+        tempDir.createSync();
+      }      
     }
     tempDirPath = new File(tempDirPath).fullPathSync();
 
     for (String subdirectory in generatedTestPath) {
       tempDirPath = '$tempDirPath/$subdirectory';
       tempDir = new Directory(tempDirPath);
       if (!tempDir.existsSync()) {
         tempDir.createSync();
       }
     }
@@ skipping 470 matching lines @@
  * $noCrash tests are expected to be flaky but not crash
  * $pass tests are expected to pass
  * $failOk tests are expected to fail that we won't fix
  * $fail tests are expected to fail that we should fix
  * $crash tests are expected to crash that we should fix
  * $timeout tests are allowed to timeout\
 """;
     print(report);
   }
 }