tools/gn: Change auto to not deduce raw pointers.

tools/gn/ninja_build_writer.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/ninja_build_writer.h"
 
 #include <stddef.h>
 
 #include <fstream>
 #include <map>
@@ skipping 224 matching lines @@
 
   for (const Pool* pool : all_pools_) {
     std::string pool_name = pool->GetNinjaName(default_toolchain_->label());
     out_ << "pool " << pool_name << std::endl
          << "  depth = " << pool->depth() << std::endl
          << std::endl;
   }
 }
 
 void NinjaBuildWriter::WriteSubninjas() {
-  for (const auto& elem : all_settings_) {
+  for (auto* elem : all_settings_) {
     out_ << "subninja ";
     path_output_.WriteFile(out_, GetNinjaFileForToolchain(elem));
     out_ << std::endl;
   }
   out_ << std::endl;
 }
 
 bool NinjaBuildWriter::WritePhonyAndAllRules(Err* err) {
   // Track rules as we generate them so we don't accidentally write a phony
   // rule that collides with something else.
@@ skipping 158 matching lines @@
   EscapeOptions ninja_escape;
   ninja_escape.mode = ESCAPE_NINJA;
 
   // Escape for special chars Ninja will handle.
   std::string escaped = EscapeString(phony_name, ninja_escape, nullptr);
 
   out_ << "build " << escaped << ": phony ";
   path_output_.WriteFile(out_, target->dependency_output_file());
   out_ << std::endl;
 }