make sure images are pushed as schema v2

On the second push to a repository in quay.io all images are converted
to schema v1. To work around this bug we build the container image
with --no-cache --squash-all. Because docker doesn't support
--squash-all we switch to use podman until the workaround is not needed
any more.

Signed-off-by: Jens Freimann <jfreimann@redhat.com>

Makefile

@@ -71,7 +71,7 @@ generate: controller-gen
 
 # Build the docker image
 docker-build: test
-	docker build . -t ${IMG}
+	podman build --squash-all --no-cache . -t ${IMG}
 
 # Push the docker image
 docker-push: