Add more phony rules to GN build

tools/gn/filesystem_utils.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 "tools/gn/filesystem_utils.h"
 
 #include <algorithm>
 
 #include "base/file_util.h"
 #include "base/logging.h"
@@ skipping 295 matching lines @@
   return !s.empty() && IsSlash(s[s.size() - 1]);
 }
 
 base::StringPiece FindDir(const std::string* path) {
   size_t filename_offset = FindFilenameOffset(*path);
   if (filename_offset == 0u)
     return base::StringPiece();
   return base::StringPiece(path->data(), filename_offset);
 }
 
+base::StringPiece FindLastDirComponent(const SourceDir& dir) {
+  const std::string& dir_string = dir.value();
+
+  if (dir_string.empty())
+    return base::StringPiece();
+  int cur = static_cast<int>(dir_string.size()) - 1;
+  DCHECK(dir_string[cur] == '/');
+  int end = cur;
+  cur--;  // Skip before the last slash.
+
+  for (; cur >= 0; cur--) {
+    if (dir_string[cur] == '/')
+      return base::StringPiece(&dir_string[cur + 1], end - cur - 1);
+  }
+  return base::StringPiece(&dir_string[0], end);
+}
+
 bool EnsureStringIsInOutputDir(const SourceDir& dir,
                                const std::string& str,
                                const Value& originating,
                                Err* err) {
   // The last char of the dir will be a slash. We don't care if the input ends
   // in a slash or not, so just compare up until there.
   //
   // This check will be wrong for all proper prefixes "e.g. "/output" will
   // match "/out" but we don't really care since this is just a sanity check.
   const std::string& dir_str = dir.value();
@@ skipping 382 matching lines @@
   return GetGenDirForSourceDir(target->settings(), target->label().dir());
 }
 
 SourceDir GetCurrentOutputDir(const Scope* scope) {
   return GetOutputDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }
 
 SourceDir GetCurrentGenDir(const Scope* scope) {
   return GetGenDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }