Do not generate multiple tests for vm options.

tools/testing/dart/test_suite.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Classes and methods for enumerating and preparing tests.
  *
  * This library includes:
  *
  * - Creating tests by listing all the Dart files in certain directories,
@@ skipping 1124 matching lines @@
              "numStaticTypeAnnotations": numStaticTypeAnnotations,
              "numCompileTimeAnnotations": numCompileTimeAnnotations };
   }
 
   List<List<String>> getVmOptions(Map optionsFromFile) {
     bool needsVmOptions = Contains(configuration['compiler'],
                                    const ['none', 'dart2dart', 'dartc']) &&
                           Contains(configuration['runtime'],
                                    const ['none', 'vm', 'drt', 'dartium']);
     if (!needsVmOptions) return [[]];
-    return optionsFromFile['vmOptions'];
+    final vmOptions = optionsFromFile['vmOptions'];
+    if (configuration['compiler'] != 'dart2dart') return vmOptions;
+    // Temporary workaround for race in test suite: tests with different
+    // vm options are still compiled into the same output file which
+    // may lead to reads from empty files.
+    return [vmOptions[0]];
   }
 }
 
 
 class DartcCompilationTestSuite extends StandardTestSuite {
   List<String> _testDirs;
   int activityCount = 0;
 
   DartcCompilationTestSuite(Map configuration,
                             String suiteName,
@@ skipping 415 matching lines @@
  * $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
  * $compileErrorSkip tests are skipped on browsers due to compile-time error
 """;
     print(report);
    }
 }