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

pkg/polymer/lib/src/barback_runner.dart

Index: pkg/polymer/lib/src/barback_runner.dart
diff --git a/pkg/polymer/lib/src/barback_runner.dart b/pkg/polymer/lib/src/barback_runner.dart
index e7a11af678172c6400fa011d5d6395fd81a16bc0..eaf637b27cc90d39aa60d3360bf2908a51de7cee 100644
--- a/pkg/polymer/lib/src/barback_runner.dart
+++ b/pkg/polymer/lib/src/barback_runner.dart
@@ -239,8 +239,10 @@ Future _addPackagesSymlinks(AssetSet assets, BarbackOptions options) {
     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);
     }
   }