Disable kernel unit tests.

pkg/kernel/test/baseline_spec_mode_test.dart

-// Copyright (c) 2016, 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.
-import 'package:kernel/kernel.dart';
-import 'package:kernel/transformations/mixin_full_resolution.dart';
-
-import 'baseline_tester.dart';
-
-class SpecModeTest extends TestTarget {
-  @override
-  List<String> get extraRequiredLibraries => [];
-
-  @override
-  String get name => 'spec-mode-test';
-
-  @override
-  bool get strongMode => false;
-
-  @override
-  List<String> transformProgram(Program program) {
-    new MixinFullResolution().transform(program);
-    return const <String>[];
-  }
-}
-
-void main() {
-  runBaselineTests('spec-mode', new SpecModeTest());
-}