OBS: do not build on ancient distributions

These were already removed in the trojita-nightly version a couple of months
ago. The versions of cmake shipped in there are too old to support Trojita.
Let's call this 0.3.96

A ton of stuff has changed since 0.3.93. I don't have much time for preparing a
release announcement, so this cannot be a "0.6", and at the same time 0.3.96
better reflects that a long time has passed since 0.3.93. And beside that,
version numbers are fun anyway.
Marking the current version as -git again