treewide: Use show_notices target for warnings

This updates all warnings currently being printed under the files_added
and build_complete targets to the show_notices target.

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: Ia14d790dd377f2892f047059b6d24e5b5c5ea823
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79423
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/payloads/Makefile.inc b/payloads/Makefile.inc
index e735443a..a2336aa 100644
--- a/payloads/Makefile.inc
+++ b/payloads/Makefile.inc
@@ -50,7 +50,7 @@
 	-$(foreach payload, $(PAYLOADS_LIST), $(MAKE) -C $(payload) print-repo-info 2>/dev/null; )
 
 ifeq ($(CONFIG_PAYLOAD_NONE),y)
-files_added:: warn_no_payload
+show_notices:: warn_no_payload
 endif
 
 warn_no_payload: