GN: Move towards only using / on Windows

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 <fstream>
 
 #include "base/command_line.h"
 #include "base/file_util.h"
@@ skipping 58 matching lines @@
     const BuildSettings* build_settings,
     const std::vector<const Settings*>& all_settings,
     const std::vector<const Target*>& default_toolchain_targets,
     std::ostream& out,
     std::ostream& dep_out)
     : build_settings_(build_settings),
       all_settings_(all_settings),
       default_toolchain_targets_(default_toolchain_targets),
       out_(out),
       dep_out_(dep_out),
-      path_output_(build_settings->build_dir(), ESCAPE_NINJA, true),
+      path_output_(build_settings->build_dir(), ESCAPE_NINJA),
       helper_(build_settings) {
 }
 
 NinjaBuildWriter::~NinjaBuildWriter() {
 }
 
 void NinjaBuildWriter::Run() {
   WriteNinjaRules();
   WriteSubninjas();
   WritePhonyAndAllRules();
@@ skipping 102 matching lines @@
       all_rules.append(" $\n    ");
     all_rules.append(target_file.value());
   }
 
   if (!all_rules.empty()) {
     out_ << "\nbuild all: phony " << all_rules << std::endl;
     out_ << "default all" << std::endl;
   }
 }