Rebase existing provisioning changes from ubuntu 16.04 to ubuntu 18.04

When the provisioning folder for ubuntu 18.04 was created in the qt5.git, it was forked from the ubuntu 16.04 folder and ported to 18.04. This took some time to integrate. In the meantime some new changes got integrated in the 16.04 folder. These changes need to be rebased to the 18.04 folder as well.

One example is this change: https://codereview.qt-project.org/#/c/234635/