clean removes @ and machine now, so no need to do it again.
Retire the '@' symlink. It isn't really needed and causes more
problems than it solves. SYSDIR is already defined almost always and
can be used instead. Working around the one case where it isn't is
much easier than working around the fact that @ may not exist in 18
other places.

Differential Revision: https://reviews.freebsd.org/D1100
These don't belong in the modules directory.