We released today a new version of the ShiningPanda plugin for Jenkins. For those who don't know this plugin yet, it provides the easiest path to setup your Python projects with Jenkins.
As a consequence, the No site packages option in Virtualenv Builder becomes System site packages and works exactly the opposite way: checking it will give the virtual environment access to the global site-packages directory. But don't worry, the plugin ensures backward compatibility.
We also fixed a 0.4 to 0.5 backward compatibility issue on declared Python installations.