Makefile: ignore time terraform has been built

Makefile

@@ -59,7 +59,7 @@ infra/backend/.terraform: \
 	$(BACKEND_TF)
 	env -C infra/backend $(TERRAFORM) init
 
-infra/main/.terraform: \
+infra/main/.terraform: | \
 	$(OUT_DIR)/terraform \
 	config/$(ENVIRONMENT).tfbackend \
 	$(MAIN_TF)
@@ -75,7 +75,7 @@ infra/backend/$(ENVIRONMENT).tfstate: \
 		-var region=$(REGION) \
 		-state ../../$@
 
-config/$(ENVIRONMENT).tfbackend: \
+config/$(ENVIRONMENT).tfbackend: | \
 	$(OUT_DIR)/terraform
 	# File is not committed and this has no shared state
 	$(MAKE) infra/backend/$(ENVIRONMENT).tfstate