makebuildserver should restart on stalled

I try to follow this guide to contribute to F-Droid: https://f-droid.org/en/docs/Submitting_to_F-Droid_Quick_Start_Guide/ (by the way in the tutorial is missing the dependency python3-vagrant)

When I run

./makebuildserver

It starts downloading the tools and stuff, but after a while ( I guess when the internet connection is gone for some minutes) it stalls.

I have to manually stop the script and start over again, where it continues fine.

But it would be perfect if the script would detect a stalled download and start over again, so I don't have to sit next to the console for hours and restart the process 20 times.

I think this is the line, where it hangs if the connection is bad:

https://gitlab.com/fdroid/fdroidserver/blob/master/makebuildserver#L432

This PR will "ease the pain" a bit: !647 (merged) but still no solution.