Update to ffmpeg 7.1.1

Switch to using ubicloud for multi arch build

ec2 spot instances kept failing too much

wip

Tag 7.0.2

Tag 7.0.1

Tag 7.0-2

Add librsvg

Turns out to be a bit messy:
librsvg needs cairo, pango and gio (glib)
cairo alpine package builds with x11 stuff
glib alpine package only has shared libraries and builds with libmount etc
and so on...

So i think only sane solution is to build some of these on our own.

Also fixes problem with git checkout commit not updating submodules
and also fixes race condition in checkelf.

TODO:
cleanup

Tag 7.0-1

Update usage to 7.0

Update readme to ffmpeg 6.1.1