Modify tests to use Directory.systemTemp

tests/standalone/io/windows_file_system_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.
 
 import 'package:expect/expect.dart';
 import "dart:io";
 import "dart:isolate";
 
 testJunctionTypeDelete() {
-  var temp = new Directory('').createTempSync();
+  var temp =
+      Directory.systemTemp.createTempSync('dart_windows_file_system_links');
   var x = '${temp.path}${Platform.pathSeparator}x';
   var y = '${temp.path}${Platform.pathSeparator}y';
 
   new Directory(x).createSync();
   new Link(y).create(x).then((_) {
     Expect.isTrue(new Directory(y).existsSync());
     Expect.isTrue(new Directory(x).existsSync());
     Expect.isTrue(FileSystemEntity.isLinkSync(y));
     Expect.isFalse(FileSystemEntity.isLinkSync(x));
     Expect.isTrue(FileSystemEntity.isDirectorySync(y));
@@ skipping 58 matching lines @@
   });
 }
 
 
 main() {
   // Links on other platforms are tested by file_system_[async_]links_test.
   if (Platform.operatingSystem == 'windows') {
     testJunctionTypeDelete();
   }
 }