Enable compiling GN by default.

tools/gn/target_unittest.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/config.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/target.h"
 #include "tools/gn/toolchain.h"
 
 namespace {
 
 class TargetTest : public testing::Test {
  public:
   TargetTest()
       : build_settings_(),
         toolchain_(Label(SourceDir("//tc/"), "tc")),
         settings_(&build_settings_, &toolchain_, std::string()) {
   }
-  ~TargetTest() {
+  virtual ~TargetTest() {
   }
 
  protected:
   BuildSettings build_settings_;
   Toolchain toolchain_;
   Settings settings_;
 };
 
 }  // namespace
 
@@ skipping 119 matching lines @@
   b_fwd.OnResolved();
   a_fwd.OnResolved();
 
   // A_fwd should now have both configs.
   ASSERT_EQ(2u, a_fwd.configs().size());
   EXPECT_EQ(&all, a_fwd.configs()[0]);
   EXPECT_EQ(&direct, a_fwd.configs()[1]);
   ASSERT_EQ(1u, a_fwd.all_dependent_configs().size());
   EXPECT_EQ(&all, a_fwd.all_dependent_configs()[0]);
 }