title: Plugins not updated when building eclipse P2 update site
body: <p>I have created an eclipse update site (using Helios) and added some features (containing my own plug-ins available in the target platform ). I then synchronized the site and build it which creates two folders: features and plugins containing the plugins and features  (.jar files).</p>
  
  <p>I then make some changes to one of the plugins in the feature, update the feature and the update site and build it again. But the resulting plugin in the plugins folder is not updated!</p>
  
  <p>How do I force the update site to produce the updated plugins in the plugins folder?</p>