Require build directories exist for some GN commands.

tools/gn/command_args.cc

Index: tools/gn/command_args.cc
diff --git a/tools/gn/command_args.cc b/tools/gn/command_args.cc
index 6ee05f7229499a5bc9b593a5577c69f813343d02..01dc8bc1b3af490c3a963d29b902c2e99021c07c 100644
--- a/tools/gn/command_args.cc
+++ b/tools/gn/command_args.cc
@@ -115,7 +115,7 @@ void PrintArgHelp(const base::StringPiece& name, const Value& value) {
 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;
@@ -233,7 +233,7 @@ int EditArgsFile(const std::string& build_dir) {
     // 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