Add test directive to include other files used by a test in its compiled output directory.

tests/standalone/io/resolve_symbolic_links_test.dart

 // Copyright (c) 2013, 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.
 //
 // Dart test program for testing FileSystemEntity.resolveSymbolicLinks
 
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 import "package:async_helper/async_helper.dart";
 import 'dart:async';
 import 'dart:io';
 
 main() {
-  String testsDir = Platform.script.resolve('../..').toFilePath();
+  String testsDir = Directory.current.uri.resolve('tests').toFilePath();
+
   // All of these tests test that resolveSymbolicLinks gives a path
   // that points to the same place as the original, and that it removes
   // all links, .., and . segments, and that it produces an absolute path.
   asyncTest(() => testFile(join(
       testsDir, 'standalone', 'io', 'resolve_symbolic_links_test.dart')));
   asyncTest(() => testFile(join(testsDir, 'standalone', 'io', '..', 'io',
                                 'resolve_symbolic_links_test.dart')));
 
   asyncTest(() => testDir(join(testsDir, 'standalone', 'io')));
   asyncTest(() => testDir(join(testsDir, 'lib', '..', 'standalone', 'io')));
@@ skipping 114 matching lines @@
     Expect.isTrue(isAbsolute(resolved));
     // Test that resolveSymbolicLinks removes all links, .., and . segments.
     Expect.isFalse(resolved.contains('..'));
     Expect.isFalse(resolved.contains('./'));
     Expect.isFalse(resolved.contains('link1'));
     return new Link(name).target()
         .then((targetName) => FileSystemEntity.identical(targetName, resolved))
         .then((identical) => Expect.isTrue(identical));
   });
 }