manifest: Tag systemd until we have btrfs headers
manifest: Tag systemd until we have btrfs headers

GNOME/gnome-ostree,vrutkovs/vrutkovs.github.io,chergert/gnome-continuous,vrutkovs/vrutkovs.github.io,GNOME/gnome-ostree,vrutkovs/vrutkovs.github.io,GNOME/gnome-ostree,chergert/gnome-continuous,chergert/gnome-continuous