busybox: add check for capabilities file

Similar to the previous commit adding a check to the init script of
umdns, do a similar change for sysntpd, just to be on the safe side.

Inspired-by: 520403cd49 ("umdns: add check for seccomp list")

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

package/utils/busybox/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=busybox
 PKG_VERSION:=1.31.1
-PKG_RELEASE:=6
+PKG_RELEASE:=7
 PKG_FLAGS:=essential
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2

package/utils/busybox/files/sysntpd

@@ -55,7 +55,7 @@ start_ntpd_instance() {
 		procd_append_param command -p $peer
 	done
 	procd_set_param respawn
-	[ -x /sbin/ujail ] && {
+	[ -x /sbin/ujail -a -e /etc/capabilities/ntpd.json ] && {
 		procd_add_jail ntpd
 		procd_set_param capabilities /etc/capabilities/ntpd.json
 		procd_set_param user ntp