Require build directories exist for some GN commands.

tools/gn/command_desc.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 <algorithm>
 #include <set>
 #include <sstream>
 
 #include "base/command_line.h"
 #include "tools/gn/commands.h"
@@ skipping 561 matching lines @@
 int RunDesc(const std::vector<std::string>& args) {
   if (args.size() != 2 && args.size() != 3) {
     Err(Location(), "You're holding it wrong.",
         "Usage: \"gn desc <out_dir> <target_name> [<what to display>]\"")
         .PrintToStdout();
     return 1;
   }
 
   // Deliberately leaked to avoid expensive process teardown.
   Setup* setup = new Setup;
-  if (!setup->DoSetup(args[0]))
+  if (!setup->DoSetup(args[0], false))
     return 1;
   if (!setup->Run())
     return 1;
 
   const Target* target = ResolveTargetFromCommandLineString(setup, args[1]);
   if (!target)
     return 1;
 
 #define CONFIG_VALUE_HANDLER(name, type) \
     } else if (what == #name) { OUTPUT_CONFIG_VALUE(name, type)
@@ skipping 125 matching lines @@
   // so always display them, even for groups and such.
   PrintLibs(target, true);
   PrintLibDirs(target, true);
 
   PrintDeps(target, true);
 
   return 0;
 }
 
 }  // namespace commands