Update compile_platform to not use dartk.

pkg/front_end/lib/src/fasta/compile_platform_dartk.dart

 // Copyright (c) 2016, 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.
 
 library fasta.compile_platform;
 
 import 'dart:async' show
     Future;
 
 import 'dart:io' show
@@ skipping 118 matching lines @@
       library.addMember(new Field(exports, isStatic: true, isConst: true,
               initializer: literal, fileUri: "${new Uri.file(source.fullName)}")
           ..fileOffset = offset);
     }
   }
 
   IOSink sink = new File.fromUri(output).openWrite();
   new BinaryPrinter(sink).writeProgramFile(program);
   await sink.close();
 }