system/cozystack-controller: add PLATFORM variable to Makefile: syntax

Signed-off-by: nbykov0 <166552198+nbykov0@users.noreply.github.com>

packages/system/cozystack-controller/Makefile

@@ -9,7 +9,7 @@ image: image-cozystack-controller update-version
 image-cozystack-controller:
 	docker buildx build -f images/cozystack-controller/Dockerfile ../../.. \
 		--provenance false \
-		--platform=$(PLATFORM)
+		--platform=$(PLATFORM) \
 		--tag $(REGISTRY)/cozystack-controller:$(call settag,$(TAG)) \
 		--cache-from type=registry,ref=$(REGISTRY)/cozystack-controller:latest \
 		--cache-to type=inline \