Leaf directories that have dependencies impacted
by options need a Makefile.depend.options file
to avoid churn in Makefile.depend

DIRDEPS for cases such as OPENSSL, TCP_WRAPPERS etc
can be set in local.dirdeps-options.mk
which can add to those set in Makefile.depend.options

See share/mk/dirdeps-options.mk

Reviewed by:	 bdrewery
MFC after:	1 week
Sponsored by:   Juniper Networks
Differential Revision:  https://reviews.freebsd.org/D22469