Ignore mkosi.builddir. In the future we can also add other patterns
if necessary.
run-intergration-tests.sh is updated to use the new script, and modified
to work from arbitrary directory.
Follow-up for #7494.
This test runs on the unified hierarchy, and ensures that cgroup
delegation works properly, i.e. writ access is granted and the requested
controllers are enabled.
Michael Biebl