Since we previously stripped down the features of `qemu_test` some of
the features users are used to while running tests through the (impure)
driver didn't work anymore. Most notably we lost support for graphical
output and audio. With this change the `driver` attribute uses are more
feature complete version of QEmu compared to the one used in the pure
Nix builds.
This gives us the best of both worlds. Users are able to see the
graphical windows of VMs while CI and regular nix builds do not have to
download all the (unnecessary) dependencies.
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