refactor makefile: minor renamings for consistency with switchbot-mqtt's Makefile

Makefile

@@ -1,7 +1,7 @@
 # sync with https://github.com/fphammerle/switchbot-mqtt/blob/master/Makefile
 
 IMAGE_NAME = docker.io/fphammerle/systemctl-mqtt
-BUILD_VERSION = $(shell git describe --match=v* --dirty | sed -e 's/^v//')
+PROJECT_VERSION = $(shell git describe --match=v* --dirty | sed -e 's/^v//')
 ARCH = $(shell arch)
 # architecture[arm_variant]
 # https://github.com/opencontainers/image-spec/blob/v1.0.1/image-index.md#image-index-property-descriptions
@@ -10,17 +10,17 @@ IMAGE_TAG_ARCH_armv6l = armv6
 IMAGE_TAG_ARCH_armv7l = armv7
 IMAGE_TAG_ARCH_x86_64 = amd64
 IMAGE_TAG_ARCH = ${IMAGE_TAG_ARCH_${ARCH}}
-IMAGE_TAG = ${BUILD_VERSION}-${IMAGE_TAG_ARCH}
+IMAGE_TAG = ${PROJECT_VERSION}-${IMAGE_TAG_ARCH}
 
 .PHONY: docker-build podman-build docker-push
 
 docker-build:
-	sudo docker build -t "${IMAGE_NAME}:${IMAGE_TAG}" .
+	sudo docker build --tag="${IMAGE_NAME}:${IMAGE_TAG}" .
 
 podman-build:
 	# --format=oci (default) not fully supported by hub.docker.com
 	# https://github.com/docker/hub-feedback/issues/1871#issuecomment-748924149
-	podman build --format=docker -t "${IMAGE_NAME}:${IMAGE_TAG}" .
+	podman build --format=docker --tag="${IMAGE_NAME}:${IMAGE_TAG}" .
 
 docker-push: docker-build
 	sudo docker push "${IMAGE_NAME}:${IMAGE_TAG}"