This adds the star of NixCon 2017 from vuizvui, slightly reformatted and
now using yants. While it has some flaws, I realized that it is ideal to
run the tests of rustSimple{Lib,Bin} where the normal and the -tests
variant would have to be rebuilt if either the tests or the library /
executable itself changes.
Change-Id: Ie8f84f98c51c9fafc046eff916c8f0df7e8f224b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2528
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>
