This is caused by the QmitkAboutDialog class which adds the curren git revision to the dialog. This means that whenever the git revision changed and CMake was run, QmitkExt rebuilds and all dependent modules/plugins are linked again. This can take some time, especially if you have many plugins activated.

Maybe we can solve this by generating an xml file which includes the git revision by CMake. This xml file can be included to the about dialog during runtime which avoids rebuilds of the QmitkExt module.