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

tools/gn/settings.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_SETTINGS_H_
 #define TOOLS_GN_SETTINGS_H_
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "tools/gn/build_settings.h"
@@ skipping 21 matching lines @@
   // The output_subdir_name is the name we should use for the subdirectory in
   // the build output directory for this toolchain's outputs. The default
   // toolchain would use an empty string (it goes in the root build dir).
   // Otherwise, it must end in a slash.
   Settings(const BuildSettings* build_settings,
            const std::string& output_subdir_name);
   ~Settings();
 
   const BuildSettings* build_settings() const { return build_settings_; }
 
+  // The actual Toolchain object pointer is not available on the settings
+  // object because it might not be resolved yet. Code running after the
+  // load is complete can ask the Builder for the Toolchain corresponding to
+  // this label.
   const Label& toolchain_label() const { return toolchain_label_; }
   void set_toolchain_label(const Label& l) { toolchain_label_ = l; }
 
   const Label& default_toolchain_label() const {
     return default_toolchain_label_;
   }
   void set_default_toolchain_label(const Label& default_label) {
     default_toolchain_label_ = default_label;
   }
 
@@ skipping 55 matching lines @@
   SourceDir toolchain_gen_dir_;
 
   Scope base_config_;
 
   bool greedy_target_generation_;
 
   DISALLOW_COPY_AND_ASSIGN(Settings);
 };
 
 #endif  // TOOLS_GN_SETTINGS_H_