Expand part declarations in the builtin library python scripts to avoid having to repeat part decla…

sdk/lib/core/corelib_sources.gypi

 # Copyright (c) 2011, 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.
 
 {
   'sources': [
     'core.dart',
-    # The above file needs to be first as it lists the parts below.
-    'bool.dart',
-    'collection.dart',
-    'comparable.dart',
-    'date_time.dart',
-    'double.dart',
-    'duration.dart',
-    'exceptions.dart',
-    'errors.dart',
-    'expando.dart',
-    'expect.dart',
-    'function.dart',
-    'identical.dart',
-    'int.dart',
-    'invocation_mirror.dart',
-    'iterable.dart',
-    'iterator.dart',
-    'map.dart',
-    'list.dart',
-    'num.dart',
-    'object.dart',
-    'options.dart',
-    'pattern.dart',
-    'print.dart',
-    'regexp.dart',
-    'set.dart',
-    'stopwatch.dart',
-    'string.dart',
-    'string_buffer.dart',
-    'string_sink.dart',
-    'type.dart',
   ],
 }