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

Also update affected Makefile.depend files.

MFC of r355616 and r355617

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

Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Sponsored by:	Dell EMC Isilon

Approved by:	re (gjb)
Sponsored by:	EMC / Isilon Storage Division

Reviewed by:	rpaulo
Approved by:	rpaulo
Relnotes:	YES
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D5916

Off by default, build behaves normally.
WITH_META_MODE we get auto objdir creation, the ability to
start build from anywhere in the tree.

Still need to add real targets under targets/ to build packages.

Differential Revision:       D2796
Reviewed by: brooks imp

Reduce overlinking

you can't use an ssh client to fetch a web page...

Submitted by:	tedu (via -tech)