Support script response files in GN.

tools/gn/substitution_writer.cc

 // Copyright 2014 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/substitution_writer.h"
 
 #include "tools/gn/build_settings.h"
 #include "tools/gn/escape.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/output_file.h"
@@ skipping 292 matching lines @@
 
 // static
 void SubstitutionWriter::WriteNinjaVariablesForSource(
     const Settings* settings,
     const SourceFile& source,
     const std::vector<SubstitutionType>& types,
     const EscapeOptions& escape_options,
     std::ostream& out) {
   for (const auto& type : types) {
     // Don't write SOURCE since that just maps to Ninja's $in variable, which
-    // is implicit in the rule.
-    if (type != SUBSTITUTION_SOURCE) {
+    // is implicit in the rule. RESPONSE_FILE_NAME is written separately
+    // only when writing target rules since it can never be used in any
+    // other context (like process_file_template).
+    if (type != SUBSTITUTION_SOURCE && type != SUBSTITUTION_RSP_FILE_NAME) {
       out << "  " << kSubstitutionNinjaNames[type] << " = ";
         EscapeStringToStream(
             out,
             GetSourceSubstitution(settings, source, type, OUTPUT_RELATIVE,
                                   settings->build_settings()->build_dir()),
             escape_options);
       out << std::endl;
     }
   }
 }
@@ skipping 222 matching lines @@
       // does not include the dot but the tool's does.
       if (target->output_extension().empty())
         return tool->default_output_extension();
       return std::string(".") + target->output_extension();
 
     default:
       NOTREACHED();
       return std::string();
   }
 }