Fix create symlink in windows by using an absolute path instead.

pkg/polymer/lib/src/barback_runner.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.
 
 /**
  * Definitions used to run the polymer linter and deploy tools without using
  * pub serve or pub deploy.
  */
 library polymer.src.barback_runner;
 
@@ skipping 221 matching lines @@
   var currentPackage = options.currentPackage;
   for (var asset in assets) {
     var id = asset.id;
     if (id.package != currentPackage) continue;
     var firstDir = _firstDir(id.path);
     if (firstDir == null) continue;
 
     if (firstDir == 'web' || (options.transformTests && firstDir == 'test')) {
       var dir = path.join(options.outDir, path.dirname(id.path));
       var linkPath = path.join(dir, 'packages');
-      var targetPath = path.relative(outPackages, from: dir);
       _deleteIfPresent(linkPath);
+      var targetPath = Platform.operatingSystem == 'windows'

[Jennifer Messerly, 2013/09/12 19:32:00]

is this a pathos bug or a dart:io bug?

(we shouldn't need platform specific checks in a pure-Dart library, IMO)

[Jennifer Messerly, 2013/09/12 19:38:08]

suggestion: remove the == 'windows' check and make the path absolute always. 

+          ? path.normalize(path.absolute(outPackages))
+          : path.normalize(path.relative(outPackages, from: dir));
       new Link(linkPath).createSync(targetPath);
     }
   }
 }
 
 /**
  * Emits a 'packages' directory directly under `out/packages` with the contents
  * of every file that was not transformed by barback.
  */
 Future _emitPackagesDir(BarbackOptions options) {
@@ skipping 63 matching lines @@
   return writer.addStream(new File(inpath).openRead())
       .then((_) => writer.close());
 }
 
 /** Write contents of an [asset] into a file at [filepath]. */
 Future _writeAsset(String filepath, Asset asset) {
   _ensureDir(path.dirname(filepath));
   var writer = new File(filepath).openWrite();
   return writer.addStream(asset.read()).then((_) => writer.close());
 }