This commit updates the weekly docker build to use `dragonfly-weekly`
image tag so that we get better separation. We also now push these
images with the github sha commit tags. We also update `latest` as
these get pushed.
- make use of docker buildx caching when possible (helpful with local docker builds)
- introduce a reusable container workflow which is triggered by docker-release and docker-weekly workflows
- added an alpine-dev Dockerfile
- split release.sh contents into different Makefile targets
- make use of job matrix to build alpine + ubuntu in parallel
- make alpine build optional by checking for Dockerfile presence
-- as the pre-built binaries don't work with alpine, because of glibc <-> musl incompatibilities
Signed-off-by: Philipp Born <git@pborn.eu>
