gn: Support build directories outside the source tree.

tools/gn/command_format.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 <sstream>
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/strings/string_split.h"
 #include "tools/gn/commands.h"
@@ skipping 689 matching lines @@
   // should all be done in parallel.
   if (args.size() != 1) {
     Err(Location(), "Expecting exactly one argument, see `gn help format`.\n")
         .PrintToStdout();
     return 1;
   }
 
   Setup setup;
   SourceDir source_dir =
       SourceDirForCurrentDirectory(setup.build_settings().root_path());
-  SourceFile file = source_dir.ResolveRelativeFile(args[0]);
+  SourceFile file = source_dir.ResolveRelativeFile(args[0],
+      setup.build_settings().root_path());
 
   std::string output_string;
   if (FormatFileToString(&setup, file, dump_tree, &output_string)) {
     bool in_place =
         base::CommandLine::ForCurrentProcess()->HasSwitch(kSwitchInPlace);
     if (in_place) {
       base::FilePath to_write = setup.build_settings().GetFullPath(file);
       printf("Writing formatted to '%s'.\n", to_write.AsUTF8Unsafe().c_str());
       if (base::WriteFile(to_write,
                           output_string.data(),
                           static_cast<int>(output_string.size())) == -1) {
         Err(Location(),
             std::string("Failed to write formatted output back to \"") +
                 to_write.AsUTF8Unsafe() + std::string("\".")).PrintToStdout();
         return 1;
       }
     } else {
       printf("%s", output_string.c_str());
     }
   }
 
   return 0;
 }
 
 }  // namespace commands