Add /boot/overlays to runtime pkg, fix distrib-dirs METALOG generation

/boot/overlays was recently added without belonging to a package. It's only
used by bootloaders at the moment, so add it to the 'runtime' package to get
added with ubldr and friends.

Fix distrib-dirs METALOG generation while we're here. History elsewhere
seems to indicate that bapt@ fixed this to pull in all attributes from
mtrees while generating the METALOG. This fix got clobbered somewhere later,
so restore it.

Reviewed by:	bapt, gjb
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D13996

etc/Makefile

@@ -379,10 +379,10 @@ distrib-dirs: ${MTREES:N/*} distrib-cleanup .PHONY
 		d=${DISTBASE}$$d; \
 		shift; \
 		test -d ${DESTDIR}/$$d || mkdir -p ${DESTDIR}/$$d; \
-		${ECHO} "${MTREE_CMD:N-W} -C -f $$m -K uname,gname | " \
+		${ECHO} "${MTREE_CMD:N-W} -C -f $$m -K all | " \
 		    "sed s#^\.#.$$d# | ${METALOG.add}" ; \
 		${MTREE_FILTER} $$m | \
-		${MTREE_CMD:N-W} -C -K uname,gname | sed s#^\.#.$$d# | \
+		${MTREE_CMD:N-W} -C -K all | sed s#^\.#.$$d# | \
 		    ${METALOG.add} ; \
 	done; true
 .endif

etc/mtree/BSD.root.dist

@@ -18,7 +18,7 @@
         ..
         modules
         ..
-        overlays
+        overlays              tags=package=runtime
         ..
         zfs
         ..