build: image: return sizes if check-size fails

Instead of just printing a warning that an image is too big, also
print both actual size and limit in the string:

WARNING: Image file somename.bin is too big: 2096101 > 1048576

Since the kernel size is checked via the same function (if
KERNEL_SIZE is specified), this will also apply to the kernel
image size check.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

include/image-commands.mk

@@ -269,8 +269,10 @@ define Build/xor-image
 endef
 
 define Build/check-size
-	@[ $$(($(subst k,* 1024,$(subst m, * 1024k,$(if $(1),$(1),$(IMAGE_SIZE)))))) -ge "$$(stat -c%s $@)" ] || { \
-		echo "WARNING: Image file $@ is too big" >&2; \
+	@imagesize="$$(stat -c%s $@)"; \
+	limitsize="$$(($(subst k,* 1024,$(subst m, * 1024k,$(if $(1),$(1),$(IMAGE_SIZE))))))"; \
+	[ $$limitsize -ge $$imagesize ] || { \
+		echo "WARNING: Image file $@ is too big: $$imagesize > $$limitsize" >&2; \
 		rm -f $@; \
 	}
 endef