ci: use manual script for distcheck build
this adds a script which reimplements the distcheck rule generated from
automake and runs that script instad of 'make distcheck'
the benefit of this is that the distcheck script can run tests multiple times
to avoid intermittent failures which could potentially cause build errors.
distcheck builds are by far the longest and most costly of all ci builds, so
it's important to reduce failure rates in these builds to the absolute minimum
in order to keep ci build times low
Differential Revision: https://phab.enlightenment.org/D6734