we're preventing now with this policy. However, these edge cases
should be rare and all that set MK_FOO directly.
WITH_FOO and WITHOUT_FOO both being defined now result in the
non-default behavior happening silently. Users needing determinism
here fall into the edge case exception for MK_FOO setting.
code from the rest. Include bsd.opts.mk in bsd.own.mk to preserve
current behavior. Future revisions will replace the inclusion of
bsd.own.mk elsewhere with bsd.opts.mk or a more appropriate new
file that's still being finalized.
