Add an output_dir override to GN.

tools/gn/target.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_TARGET_H_
 #define TOOLS_GN_TARGET_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 82 matching lines @@
   //
   // Because this depends on the tool for this target, the toolchain must
   // have been set before calling.
   std::string GetComputedOutputName() const;
 
   bool output_prefix_override() const { return output_prefix_override_; }
   void set_output_prefix_override(bool prefix_override) {
     output_prefix_override_ = prefix_override;
   }
 
+  // Desired output directory for the final output. This will be used for
+  // the {{output_dir}} substitution in the tool if it is specified. If
+  // is_null, the tool default will be used.
+  const SourceDir& output_dir() const { return output_dir_; }
+  void set_output_dir(const SourceDir& dir) { output_dir_ = dir; }
+
   // The output extension is really a tri-state: unset (output_extension_set
   // is false and the string is empty, meaning the default extension should be
   // used), the output extension is set but empty (output should have no
   // extension) and the output extension is set but nonempty (use the given
   // extension).
   const std::string& output_extension() const { return output_extension_; }
   void set_output_extension(const std::string& extension) {
     output_extension_ = extension;
     output_extension_set_ = true;
   }
@@ skipping 212 matching lines @@
   bool CheckVisibility(Err* err) const;
   bool CheckTestonly(Err* err) const;
   bool CheckNoNestedStaticLibs(Err* err) const;
   bool CheckAssertNoDeps(Err* err) const;
   void CheckSourcesGenerated() const;
   void CheckSourceGenerated(const SourceFile& source) const;
 
   OutputType output_type_;
   std::string output_name_;
   bool output_prefix_override_;
+  SourceDir output_dir_;
   std::string output_extension_;
   bool output_extension_set_;
 
   FileList sources_;
   bool all_headers_public_;
   FileList public_headers_;
   bool check_includes_;
   bool complete_static_lib_;
   bool testonly_;
   FileList inputs_;
@@ skipping 41 matching lines @@
   // Output files. Empty until the target is resolved.
   std::vector<OutputFile> computed_outputs_;
   OutputFile link_output_file_;
   OutputFile dependency_output_file_;
   OutputFile runtime_link_output_file_;
 
   DISALLOW_COPY_AND_ASSIGN(Target);
 };
 
 #endif  // TOOLS_GN_TARGET_H_