Makefile: introduce check-package target

The snippet of code that runs a check-package on all
.mk/.hash/Config.in files is currently only available within
.gitlab-ci.yml, and isn't immediately and easily usable by Buildroot
users. In order to simplify this, this commit introduces a top-level
"check-package" make target that implements the same logic. The
.gitlab-ci.yml file is changed to use "make check-package".

Since this target is oriented towards Buildroot developers, we
intentionally do not clutter the already noisy "make help" text with
this additional make target.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
diff --git a/Makefile b/Makefile
index f79d39f..c4ed458 100644
--- a/Makefile
+++ b/Makefile
@@ -130,7 +130,7 @@
 noconfig_targets := menuconfig nconfig gconfig xconfig config oldconfig randconfig \
 	defconfig %_defconfig allyesconfig allnoconfig alldefconfig silentoldconfig release \
 	randpackageconfig allyespackageconfig allnopackageconfig \
-	print-version olddefconfig distclean manual manual-%
+	print-version olddefconfig distclean manual manual-% check-package
 
 # Some global targets do not trigger a build, but are used to collect
 # metadata, or do various checks. When such targets are triggered,
@@ -1125,6 +1125,10 @@
 print-version:
 	@echo $(BR2_VERSION_FULL)
 
+check-package:
+	find $(TOPDIR) -type f \( -name '*.mk' -o -name '*.hash' -o -name 'Config.*' \) \
+		-exec ./utils/check-package {} +
+
 .PHONY: .gitlab-ci.yml
 .gitlab-ci.yml: .gitlab-ci.yml.in
 	cp $< $@