Its purpose was as a convenient way to make the full set of test
output files from inputs/test.but, _even_ the one that needed help
from a Windows (or close enough) build machine to run HHC. But now we
can generate CHM directly, the latter is not necessary, so this build
script is no longer doing anything you can't do just as easily by just
running 'halibut inputs/test.but'.

'bob -s Buildscr.test' builds Halibut, runs it over inputs/test.but to
produce all the supported output formats, and delivers them all into
the output directory. Including Windows HTML Help, for which it has to
do a special run of the HTML back end with extra options and then get
a Windows box to run hhc (hence this having to be a Buildscr).