pkgbase: Create a FreeBSD-mtree package

And put the mtree binary and files in it.
Useful to create small mfsroot using /etc/rc.d/var without
having to install FreeBSD-utilities.

MFC after:	2 weeks
Sponsored by:	Beckhoff Automation GmbH & Co. KG
Differential Revision:	https://reviews.freebsd.org/D33442

etc/mtree/Makefile

@@ -2,6 +2,8 @@
 
 .include <src.opts.mk>
 
+PACKAGE=	mtree
+
 # NOTE: BSD.debug.dist is unconditionally installed for developer ease-of-use.
 FILES=	\
 	BSD.debug.dist \

release/packages/Makefile.package

@@ -75,6 +75,8 @@ manuals_COMMENT= 	Manual Pages
 manuals_DESC= 		Manual Pages
 mlx-tools_COMMENT=	Mellanox Utilities
 mlx-tools_DESC=		Mellanox Utilities
+mtree_COMMENT=		MTREE Files
+mtree_DESC=		MTREE Files
 nfs_COMMENT=		NFS Utilities
 nfs_DESC= 		NFS Utilities
 openssl_COMMENT=	OpenSSL Library and Utility

usr.sbin/nmtree/Makefile

@@ -4,6 +4,8 @@
 
 .PATH: ${SRCTOP}/contrib/mtree
 
+PACKAGE=	mtree
+
 PROG=		mtree
 MAN=		mtree.5 mtree.8
 SRCS=		compare.c crc.c create.c excludes.c getid.c misc.c mtree.c \