buildserver: remove Qt installer, its huge, outdated, and being replaced
The currently included Qt has known security issues and is outdated. This can now be replaced by downloading and installing the Qt installer using the sudo= build field. @relan's provisioner system will also replace this once that's done. There are only two apps that currently use the Qt stuff:
- csd.qtproject.minesweeper
- org.openorienteering.mapper