Do not generate multiple tests for vm options.

tools/testing/dart/test_suite.dart

Index: tools/testing/dart/test_suite.dart
diff --git a/tools/testing/dart/test_suite.dart b/tools/testing/dart/test_suite.dart
index 50c7d30ac980a4dd98456e945b96d92b5840206b..fe37d722c38f5aa5c42de8e02b527435b131e1c5 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -1142,7 +1142,12 @@ class StandardTestSuite implements TestSuite {
                           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]];
   }
 }