Drop rc_sys definition from build system

etc/Makefile

@@ -24,14 +24,5 @@ SED_EXTRA=	${SED_EXTRA-${OS}}
 
 include ${MK}/scripts.mk
 
-# We can't use "ifndef" here because that treats set-but-empty
-# as not-set which is not what we want
-MKRCSYS ?= automagicplease
-ifeq (${MKRCSYS},automagicplease)
-# If the user isn't picking a default, then have the
-# config go with runtime automagic detection #357247
-rc.conf: SED_EXTRA += -e '/^rc_sys=""/s:^:\#:'
-MKRCSYS =
-endif
 rc.conf: rc.conf.in rc.conf.${OS}
 	${SED} ${SED_REPLACE} ${SED_EXTRA} $^ > $@