Makefile.mk: Use Wcast-function-type GCC option

Change-Id: I25415d7fd82879889ffaa1bb534ad5d0b174854e
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/82736
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/Makefile.mk b/Makefile.mk
index 7be4685..a16089d 100644
--- a/Makefile.mk
+++ b/Makefile.mk
@@ -529,6 +529,7 @@
 ifeq ($(CONFIG_COMPILER_GCC),y)
 CFLAGS_common += -Wold-style-declaration
 CFLAGS_common += -Walloc-size
+CFLAGS_common += -Wcast-function-type
 # Don't add these GCC specific flags when running scan-build
 ifeq ($(CCC_ANALYZER_OUTPUT_FORMAT),)
 CFLAGS_common += -Wno-packed-not-aligned