Stopped symlink code creating extra dirs.

Previously, trying to create a symlink of packages -> cache/package/lib
would create packages/lib. Now it will copy cache/package/lib to
packages doing the rename step at the same time.

R=tapted@chromium.org

Committed: https://github.com/tapted/bleeding_edge/commit/8a2311c

Review URL: https://codereview.appspot.com/54920043