Fix for unavailable dev-help and pkg-help targets

Fixes: a94d74d9c875b ("rework prereq check")
Signed-off-by: Phil Sutter <phil@nwl.cc>

Makefile

@@ -4,5 +4,5 @@
 # GNU make and BSD make compatible make file wrapper
 MAKECMDGOALS+= ${.TARGETS}
 
-all v allmodconfig allnoconfig allyesconfig help targethelp kernelconfig image menuconfig defconfig oldconfig download clean cleankernel cleansystem cleandir distclean hostclean hostpackage fetch package extract patch dep menu newpackage host-update-patches update-patches:
+all v allmodconfig allnoconfig allyesconfig help pkg-help dev-help targethelp kernelconfig image menuconfig defconfig oldconfig download clean cleankernel cleansystem cleandir distclean hostclean hostpackage fetch package extract patch dep menu newpackage host-update-patches update-patches:
 	@./scripts/prereq.sh ${MAKECMDGOALS}