cmake and MANDIR

[Greg Troxel <gdt%lexort.com@localhost>]

I am working on packaging mosquitto (in wip), which uses cmake.  There
is a patch to the CMakeLists.txt file to adjust MANDIR, and this works
on NetBSD which puts man in $prefix/man/man1.  But on MacOS, it's
$prefix/share/man/man1, and pkgsrc automatically and mysteriously
changes the PLIST.

With autoconf, there's a standard interface to control man location, and
pkgsrc obviously uses it.

Reading a bit about cmake, my impression is that people write cmake code
for these things, and do it differently, and thus there is no standard
way for pkgsrc to ask cmake-using programs to put man pages in the right
place.

So any given program might need a patch to CmakeLists.txt to make it
respect an env variable, and then a env/arg line in the pkgsrc Makefile
to pass in mandir.

Can anyone explain how this is supposed to work?