We currently don't build systemd for armhf anymore. Disable all other
packages in the systemd repo too, as these can't be built without the
systemd dependency.
FWIW all of Phosh, Gnome Mobile and Plasma Mobile already have major
packages not building for armhf so they couldn't be used on this arch
anyway.
Once pmb issue 2618 is resolved, we can re-enable systemd for armhf.
Co-authored-by: Oliver Smith <ollieparanoid@postmarketos.org>
Related to !6637Fixes#3783
[ci:skip-build], [ci:skip-vercheck]: changing arch= only
Part-of: https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/6710