Move dartk to the tool folder

pkg/kernel/bin/reified_dart.dart

 #!/usr/bin/env dart
 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:io';
 
 import 'package:args/args.dart' as args;
 import 'package:path/path.dart' as path;
 
 args.ArgParser parser = new args.ArgParser(allowTrailingOptions: true)
   ..addOption("sdk",
       abbr: "s",
       help: "Path to the Dart SDK. By default it will be searched at the path\n"
           "'../../../out/ReleaseX64/patched_sdk' relative to the directory\n"
           "of 'reified_dart'.",
       defaultsTo: null)
   ..addOption("dartk",
       abbr: "k",
       help: "Path to 'dartk' executable. By default it will be searched for\n"
-          "in the same directory as 'reified_dart'.",
+          "in the tool directory of the kernel package.",
       defaultsTo: null)
   ..addOption("dill-output",
       abbr: "d",
       help: "Path to intermediate reified .dill file. If not specified,\n"
           "the intermediate file is created in a temporary location\n"
           "and is removed after program execution.",
       defaultsTo: null);
 
 String getUsage() => """
 Usage: reified_dart [options] FILE
@@ skipping 58 matching lines @@
   checkIsDirectory(sdkPath,
       option: "Path to Dart SDK",
       description: "The --sdk option wasn't specified, "
           "so default location was checked.");
 
   return sdkPath;
 }
 
 String getDefaultDartk() {
   String currentFile = Platform.script.toFilePath();
-  String dartkPath = path.join(path.dirname(currentFile), "dartk.dart");
+  String dartkPath = path.join(path.dirname(currentFile), "../tool/dartk.dart");
 
   checkIsFile(dartkPath,
       option: "Path to 'dartk'",
       description: "The --dartk option wasn't specified, "
           "so default location was checked.");
 
   return dartkPath;
 }
 
 main(List<String> arguments) async {
@@ skipping 54 matching lines @@
 
   stdout.write(result.stdout);
   stderr.write(result.stderr);
   tempFile?.parent?.delete(recursive: true);
   if (result.exitCode != 0) {
     stderr.writeln("ERROR: execution of 'dart' failed with exit code "
         "${result.exitCode}");
     exit(result.exitCode);
   }
 }