Require build directories exist for some GN commands.

tools/gn/command_args.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 <stdio.h>
 #include <stdlib.h>
 
 #include <map>
 
 #include "base/command_line.h"
@@ skipping 97 matching lines @@
     GetContextForValue(value, &location, &comment);
     OutputString("    " + location + "\n" + comment);
   } else {
     OutputString("    (Internally set)\n");
   }
 }
 
 int ListArgs(const std::string& build_dir) {
   Setup* setup = new Setup;
   setup->set_check_for_bad_items(false);
-  if (!setup->DoSetup(build_dir) || !setup->Run())
+  if (!setup->DoSetup(build_dir, false) || !setup->Run())
     return 1;
 
   Scope::KeyValueMap build_args;
   setup->build_settings().build_args().MergeDeclaredArguments(&build_args);
 
   // Find all of the arguments we care about. Use a regular map so they're
   // sorted nicely when we write them out.
   std::map<base::StringPiece, Value> sorted_args;
   std::string list_value =
       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(kSwitchList);
@@ skipping 97 matching lines @@
 
 int EditArgsFile(const std::string& build_dir) {
   {
     // Scope the setup. We only use it for some basic state. We'll do the
     // "real" build below in the gen command.
     Setup setup;
     setup.set_check_for_bad_items(false);
     // Don't fill build arguments. We're about to edit the file which supplies
     // these in the first place.
     setup.set_fill_arguments(false);
-    if (!setup.DoSetup(build_dir))
+    if (!setup.DoSetup(build_dir, true))
       return 1;
 
     // Ensure the file exists. Need to normalize path separators since on
     // Windows they can come out as forward slashes here, and that confuses some
     // of the commands.
     base::FilePath arg_file =
         setup.build_settings().GetFullPath(setup.GetBuildArgFile())
         .NormalizePathSeparators();
     if (!base::PathExists(arg_file)) {
       std::string argfile_default_contents =
@@ skipping 91 matching lines @@
         "Or see \"gn help args\" for more variants.").PrintToStdout();
     return 1;
   }
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(kSwitchList))
     return ListArgs(args[0]);
   return EditArgsFile(args[0]);
 }
 
 }  // namespace commands