Add script docker-entrypoint.sh to shellcheck and try to _simplify_ and
_normalize_ some parts:
- fix issues reported by shellcheck
- don't mix tab and space indent
- command 'help' replaced by '-h': ./dockerfiles/docker-entrypoint.sh -h
- replace printf in help() by 'cat <<EOF'
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
make docker.buildx : build and push multiarch build.
(it can't be only build)
use buildx with the --cache-from and --cache-to options to cache the layers
(only the last built is cached)
