feat: add runit support

assets/services/runit/conf

@@ -0,0 +1,5 @@
+BAUD_RATE=38400
+TERM_NAME=linux
+
+TTY=tty7
+EXEC_PATH=/bin/lidm

assets/services/runit/finish

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+[ -r conf ] && . ./conf
+
+exec utmpset -w $TTY

assets/services/runit/run

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+[ -r conf ] && . ./conf
+
+if [ -x /sbin/getty -o -x /bin/getty ]; then
+	# busybox
+	GETTY=getty
+elif [ -x /sbin/agetty -o -x /bin/agetty ]; then
+	# util-linux
+	GETTY=agetty
+fi
+
+exec setsid ${GETTY} ${GETTY_ARGS} \
+	"${TTY}" "${TERM_NAME}" \
+	-n -l "${EXEC_PATH}" -o 7