Turns out we can, apart from just building the module, "shove" it into
the SELinux database in a chroot as well. This brings quite significant
time savings, as the SELinux db rebuild takes 2 - 5 minutes in a VM
without acceleration (and takes currently ~half of the runtime of the test
in the C8S job).
Let's save some time and build the SELinux test module on the host
instead of a possibly unaccelerated VM. This brings the runtime of
TEST-06-SELINUX from ~12 minutes down to a ~1 minute.
Those are all consumed by our parser, so they all support comments.
I was considering whether they should have a license header at all,
but in the end I decided to add it because those files are often created
by copying parts of real unit files. And if the real ones have a license,
then those might as well. It's easier to add it than to make an exception.
