Implement tracking of BUILD.gn files used to define target, toolchain or

tools/gn/filesystem_utils_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 "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/platform_thread.h"
@@ skipping 751 matching lines @@
                 default_context, SourceDir("/C:/abs"), BuildDirType::GEN)
                 .value());
 #endif
 }
 
 TEST(FilesystemUtils, GetBuildDirForTarget) {
   BuildSettings build_settings;
   build_settings.SetBuildDir(SourceDir("//out/Debug/"));
   Settings settings(&build_settings, "");
 
-  Target a(&settings, Label(SourceDir("//foo/bar/"), "baz"));
+  Target a(&settings, Label(SourceDir("//foo/bar/"), "baz"), {});
   EXPECT_EQ("//out/Debug/obj/foo/bar/",
             GetBuildDirForTargetAsSourceDir(&a, BuildDirType::OBJ).value());
   EXPECT_EQ("obj/foo/bar/",
             GetBuildDirForTargetAsOutputFile(&a, BuildDirType::OBJ).value());
   EXPECT_EQ("//out/Debug/gen/foo/bar/",
             GetBuildDirForTargetAsSourceDir(&a, BuildDirType::GEN).value());
   EXPECT_EQ("gen/foo/bar/",
             GetBuildDirForTargetAsOutputFile(&a, BuildDirType::GEN).value());
 }
 
@@ skipping 14 matching lines @@
             GetBuildDirAsSourceDir(context, BuildDirType::OBJ).value());
 
   EXPECT_EQ("",
             GetBuildDirAsOutputFile(context, BuildDirType::TOOLCHAIN_ROOT)
                 .value());
   EXPECT_EQ("gen/",
             GetBuildDirAsOutputFile(context, BuildDirType::GEN).value());
   EXPECT_EQ("obj/",
             GetBuildDirAsOutputFile(context, BuildDirType::OBJ).value());
 }