The N_host_libs dance only makes sense if host is FreeBSD.
Even then, if MK_host_egacy is yes we need libmd
libnetbsd does not need libutil when using libegacy
Sponsored by: Juniper Networks, Inc.
Add Makefile.depend.options to libnetbsd, mkimg and makefs
to ensure libegacy is build if needed.
targets/pseudo/stage/Makefile avoid the need for mtree
the staging process creates target dirs as needed anyway.
Reviewed by: stevek
Sponsored by: Juniper Networks, Inc.
Differential Revision: https://reviews.freebsd.org/D39757