GN: use the correct directory for self-invocation.

tools/gn/ninja_build_writer.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 "tools/gn/ninja_build_writer.h"
 
 #include <stddef.h>
 
 #include <fstream>
 #include <map>
@@ skipping 34 matching lines @@
 
   // The last one we encountered.
   const Target* last_seen;
 };
 
 std::string GetSelfInvocationCommand(const BuildSettings* build_settings) {
   base::FilePath executable;
   PathService::Get(base::FILE_EXE, &executable);
 
   base::CommandLine cmdline(executable.NormalizePathSeparatorsTo('/'));
+
+  // Use "." for the directory to generate. When Ninja runs the command it
+  // will have the build directory as the current one. Coding it explicitly
+  // will cause everything to get confused if the user renames the directory.
   cmdline.AppendArg("gen");
-  cmdline.AppendArg(build_settings->build_dir().value());
+  cmdline.AppendArg(".");
+
   cmdline.AppendSwitchPath(std::string("--") + switches::kRoot,
                            build_settings->root_path());
   // Successful automatic invocations shouldn't print output.
   cmdline.AppendSwitch(std::string("-") + switches::kQuiet);
 
   EscapeOptions escape_shell;
   escape_shell.mode = ESCAPE_NINJA_COMMAND;
 #if defined(OS_WIN)
   // The command line code quoting varies by platform. We have one string,
   // possibly with spaces, that we want to quote. The Windows command line
@@ skipping 379 matching lines @@
   EscapeOptions ninja_escape;
   ninja_escape.mode = ESCAPE_NINJA;
 
   // Escape for special chars Ninja will handle.
   std::string escaped = EscapeString(phony_name, ninja_escape, nullptr);
 
   out_ << "build " << escaped << ": phony ";
   path_output_.WriteFile(out_, target->dependency_output_file());
   out_ << std::endl;
 }