Add an output_dir override to GN.

tools/gn/ninja_binary_target_writer.h

 // 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.
 
 #ifndef TOOLS_GN_NINJA_BINARY_TARGET_WRITER_H_
 #define TOOLS_GN_NINJA_BINARY_TARGET_WRITER_H_
 
 #include "base/macros.h"
 #include "tools/gn/config_values.h"
 #include "tools/gn/ninja_target_writer.h"
@@ skipping 81 matching lines @@
   void WriteCompilerBuildLine(const SourceFile& source,
                               const std::vector<OutputFile>& extra_deps,
                               const OutputFile& order_only_dep,
                               Toolchain::ToolType tool_type,
                               const std::vector<OutputFile>& outputs);
 
   void WriteLinkerStuff(const std::vector<OutputFile>& object_files,
                         const std::vector<SourceFile>& other_files);
   void WriteLinkerFlags(const SourceFile* optional_def_file);
   void WriteLibs();
-  void WriteOutputExtension();
+  void WriteOutputSubstitutions();
   void WriteSolibs(const std::vector<OutputFile>& solibs);
 
   // Writes the stamp line for a source set. These are not linked.
   void WriteSourceSetStamp(const std::vector<OutputFile>& object_files);
 
   // Gets all target dependencies and classifies them, as well as accumulates
   // object files from source sets we need to link.
   void GetDeps(UniqueVector<OutputFile>* extra_object_files,
                UniqueVector<const Target*>* linkable_deps,
                UniqueVector<const Target*>* non_linkable_deps) const;
@@ skipping 26 matching lines @@
   const Tool* tool_;
 
   // Cached version of the prefix used for rule types for this toolchain.
   std::string rule_prefix_;
 
   DISALLOW_COPY_AND_ASSIGN(NinjaBinaryTargetWriter);
 };
 
 #endif  // TOOLS_GN_NINJA_BINARY_TARGET_WRITER_H_