The CI job has the x86_64 tag, but no runners with this tag are available
currently. Let's try to drop it.

Closes #19

The GIT system doesn't support empty directories and the test suite
fails currently when the reference directory is missing. But there is
a need to add test with an empty reference directory. Let's make some
changes so the missing reference directory is handled as empty.

This will correctly indicate that bzip2 tar balls are supported when
shared-mime-info <2.4 where the alias between the tar and normal types
is not set.

Fixes: https://gitlab.gnome.org/GNOME/nautilus/-/issues/3494

Restoring user, group, and unix mode might be problematic in terms of
security. The libarchive's `archive_write_disk` API doesn't restore user,
group, SUID, SGID, nor sticky bit by default for this reason. It also
honors umask settings. Let's do the same here. If somebody needs that
functionality in gnome-autoar, an extra flag needs to be added.

Related: https://bugzilla.redhat.com/show_bug.cgi?id=2231176

This reverts commit 643139bf