GN: don't write separate files for non-binary targets

tools/gn/xcode_writer.h

 // Copyright 2016 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_XCODE_WRITER_H_
 #define TOOLS_GN_XCODE_WRITER_H_
 
 #include <iosfwd>
 #include <map>
 #include <memory>
@@ skipping 30 matching lines @@
   // |ninja_extra_args| are additional arguments to pass to ninja invocation
   // (can be used to increase limit of concurrent processes when using goma).
   // |dir_filters_string| is optional semicolon-separated list of label patterns
   // used to limit the set of generated projects. Only matching targets will be
   // included to the workspace. On failure will populate |err| and return false.
   static bool RunAndWriteFiles(const std::string& workspace_name,
                                const std::string& root_target_name,
                                const std::string& ninja_extra_args,
                                const std::string& dir_filters_string,
                                const BuildSettings* build_settings,
-                               Builder* builder,
+                               const Builder& builder,
                                Err* err);
 
  private:
   XcodeWriter(const std::string& name);
   ~XcodeWriter();
 
   // Filters the list of targets to only return the targets with artifacts
   // usable from Xcode (mostly application bundles). On failure populate |err|
   // and return false.
   static bool FilterTargets(const BuildSettings* build_settings,
@@ skipping 31 matching lines @@
   void WriteWorkspaceContent(std::ostream& out);
   void WriteProjectContent(std::ostream& out, PBXProject* project);
 
   std::string name_;
   std::vector<std::unique_ptr<PBXProject>> projects_;
 
   DISALLOW_COPY_AND_ASSIGN(XcodeWriter);
 };
 
 #endif  // TOOLS_GN_XCODE_WRITER_H_