1. Replace all "groff"'s with $GROFF so the right binary is picked up depending
on new or old toolchain setups and USETOOLS
2. Remove the DESTDIR check where it adds -M. This is pointless as some of the
file in share/tmac have hard coded references to /usr/share/tmac so using the
new ones in $DESTDIR will just point you back into /usr/share anyways...
(the new toolchain has no issue here as it's tmac files all point into
$TOOLDIR. Any old setups should just depend on the local setup instead of
some mix of DESTDIR and old files the -M would have produced).
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