Unconditionally copy the build host /etc/resolv.conf into
the chroot directory, since hostname resolution may be
needed in the case of building a dvd image (with packages)
and also setting 'NOPORTS=1'.

MFC after:	3 days
X-MFC-With:	r258305, r258307
Sponsored by:	The FreeBSD Foundation
Set the PKG_CACHEDIR directory to 'dvd/' instead of 'release/'
in preparation of adding a 'dvd1.iso' target.

MFC after:	3 days
X-MFC-With:	r258305, r258307, r258308
Sponsored by:	The FreeBSD Foundation