Text versions of manpages do not need to be generated for normal
installations, they're only used for generating HTML and our
amazing, award-winning homepage.
We'll also rely on touch(1) instead of Perl utime to benefit
users w/o git-set-file-times in txt2pre. Perl numeric values
cannot represent nanosecond resolution accurately even with
Time::HiRes; which causes nanosecond-aware make(1)
implementations to repeatedly rebuild.