Clone the osmo-ttcn3-hacks and all dependency repositories less often by
moving related commands to the shared debian-stretch-titan image.
Remove the 'git checkout -f -B master origin/master' line, because the
master branch is checked out by default.
While at it, move the shared "git config" commands too, and move them
before cloning the repositories, so they don't run again whenever the
deps change (logic to invalidate the cache if deps change will be added
in the next patch).
Remove leftover from old TTCN-3 build scripts, before refactoring ttcn3
Dockerfiles. This line has already been removed in 357ec806 from 2017 for
In osmo-ttcn3-hacks.git, this is only referenced in the obsolete
bin/install.script (looks like we could remove that, together with the
rest of the bin dir?).