Support script response files in GN.

tools/gn/function_write_file.cc

 // 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.
 
 #include <iostream>
 #include <sstream>
 
 #include "base/files/file_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
@@ skipping 64 matching lines @@
     "\n"
     "  write_file(filename, data)\n"
     "\n"
     "  If data is a list, the list will be written one-item-per-line with no\n"
     "  quoting or brackets.\n"
     "\n"
     "  If the file exists and the contents are identical to that being\n"
     "  written, the file will not be updated. This will prevent unnecessary\n"
     "  rebuilds of targets that depend on this file.\n"
     "\n"
+    "  One use for write_file is to write a list of inputs to an script\n"
+    "  that might be too long for the command line. However, it is\n"
+    "  preferrable to use response files for this purpose. See\n"
+    "  \"gn help response_file_contents\".\n"
+    "\n"
     "  TODO(brettw) we probably need an optional third argument to control\n"
     "  list formatting.\n"
     "\n"
-    "Arguments:\n"
+    "Arguments\n"
     "\n"
     "  filename\n"
     "      Filename to write. This must be within the output directory.\n"
     "\n"
     "  data:\n"
     "      The list or string to write.\n";
 
 Value RunWriteFile(Scope* scope,
                    const FunctionCallNode* function,
                    const std::vector<Value>& args,
@@ skipping 54 matching lines @@
   if (DoWriteFile(file_path, new_contents.c_str(), int_size)
       != int_size) {
     *err = Err(function->function(), "Unable to write file.",
                "I was writing \"" + FilePathToUTF8(file_path) + "\".");
     return Value();
   }
   return Value();
 }
 
 }  // namespace functions