remove docgen source and targets from build

pkg/docgen/test/metadata_test.dart

-// Copyright (c) 2014, 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 async_await_test;
-
-import 'dart:io';
-
-import 'package:path/path.dart' as path;
-import 'package:unittest/unittest.dart';
-
-import '../lib/src/exports/mirrors_util.dart' as dart2js_util;
-import '../lib/src/models/annotation.dart';
-import '../lib/docgen.dart';
-
-const Map<String, String> SOURCES = const <String, String>{
-  'main.dart': '''
-import 'lib.dart' as lib;
-
-@lib.Annotation("foo", 42)
-main() {
-}
-''',
-  'lib.dart': '''
-class Annotation {
-  final String arg1;
-  final int arg2;
-  const Annotation(this.arg1, this.arg2);
-}
-'''};
-
-main() {
-  group('Generate docs for', () {
-    test('files with annotations', () {
-      var temporaryDir = Directory.systemTemp.createTempSync('metadata_');
-      var uris = <Uri>[];
-      SOURCES.forEach((name, code) {
-        var fileName = path.join(temporaryDir.path, name);
-        var file = new File(fileName);
-        file.writeAsStringSync(code);
-        uris.add(new Uri.file(fileName));
-      });
-
-      return getMirrorSystem(uris, false).then((mirrorSystem) {
-        var library = new Library(mirrorSystem.libraries[uris[0]]);
-        expect(library is Library, isTrue);
-
-        var main = library.functions['main'];
-        expect(main is Method, isTrue);
-
-        var annotations = main.annotations;
-        expect(annotations.length, equals(1));
-
-        var annotation = annotations[0];
-        expect(annotation is Annotation, isTrue);
-
-        var map = annotation.toMap();
-        expect(map['name'], equals('lib-dart.Annotation.Annotation-'));
-        expect(map['parameters'].length, equals(2));
-        expect(map['parameters'][0], equals('"foo"'));
-        expect(map['parameters'][1], equals('42'));
-      }).whenComplete(() => temporaryDir.deleteSync(recursive: true));
-    });
-  });
-}