Add support for runit

X-Gentoo-Bug: 501364
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=501364

init.d/Makefile

@@ -3,7 +3,8 @@ include ../mk/net.mk
 DIR=	${INITDIR}
 SRCS=	bootmisc.in fsck.in hostname.in local.in localmount.in loopback.in \
 	netmount.in osclock.in root.in savecache.in swap.in swapfiles.in \
-	tmpfiles.setup.in swclock.in sysctl.in urandom.in s6-svscan.in ${SRCS-${OS}}
+	tmpfiles.setup.in swclock.in sysctl.in runsvdir.in urandom.in \
+	s6-svscan.in ${SRCS-${OS}}
 BIN=	${OBJS}
 
 # Are we installing our network scripts?