core: also display the custom help with our main help

The patch merges the custom help, introduced in the previous patch, at
the end of our internal help.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Jérôme Pouiller <jezz@sysmic.org>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Makefile

@@ -893,7 +893,9 @@ endif
 	rm -rf $(BR2_CONFIG) $(CONFIG_DIR)/.config.old $(CONFIG_DIR)/..config.tmp \
 		$(CONFIG_DIR)/.auto.deps $(BR2_EXTERNAL_FILE)
 
-help:
+help: help-internal help-custom
+
+help-internal:
 	@echo 'Cleaning:'
 	@echo '  clean                  - delete all files created by build'
 	@echo '  distclean              - delete all non-source files (including .config)'
@@ -966,7 +968,6 @@ endif
 	@echo '  source-check           - check selected packages for valid download URLs'
 	@echo '  external-deps          - list external packages used'
 	@echo '  legal-info             - generate info about license compliance'
-	@echo '  help-custom            - print help about custom actions (if any)'
 	@echo
 	@echo '  make V=0|1             - 0 => quiet build (default), 1 => verbose build'
 	@echo '  make O=dir             - Locate all output files in "dir", including .config'