Makefile: Add help to nobuild_targets

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Makefile

@@ -94,7 +94,7 @@ noconfig_targets := menuconfig nconfig gconfig xconfig config oldconfig randconf
 # something else than one of the nobuild_targets.
 nobuild_targets := source source-check \
 	legal-info external-deps _external-deps \
-	clean distclean
+	clean distclean help
 ifeq ($(MAKECMDGOALS),)
 BR_BUILDING = y
 else ifneq ($(filter-out $(nobuild_targets),$(MAKECMDGOALS)),)