make this an oci container, not nspawn

Makefile

@@ -0,0 +1,19 @@
+OUTPUT	?= $(USER)/bip
+CTR	?= podman
+IMAGE	?= fedora
+TAG	?= 29
+
+.PHONY: image
+image: .digest
+	$(CTR) build \
+		--build-arg "IMAGE=$(IMAGE)" \
+		--build-arg "IMAGE_TAG=$(TAG)" \
+		--build-arg "DIGEST=$(shell cat .digest)" \
+		-t $(OUTPUT) \
+		.
+
+pull:
+	$(CTR) pull $(IMAGE):$(TAG)
+
+.digest: pull
+	$(CTR) images --digests --format "{{.Digest}}" $(IMAGE):$(TAG) | head -1 | tee $@