It's a pain to make gitlab clear it on Gluon updates, so it's more
harmful than useful. Just get rid off it and accept the increased build
times.

Add a script which allows generating the target list for copy-pasting to
.gitlab-ci.yaml

this adds support for devices with cellular modems, like the GL-inet
XE300

Some devices (e.g. TP-Link RE450) only have 6 MB available space. That's
not enough to hold all the stuff e.g. ca-certs. So only build
ca-certificates, airtime stats etc. when we have enough flash.

For now, leave gitlab.freifunk-stuttgart.de in place

We were expecting a checked out branch which obviously isn't always the
case. Instread try and find a tag.