PR#489 (01430603b6) introduced dumb-init for better
signals handling.
While this has the intended effect, it was done ny downloading the dumb-init static bin
into the image… only using the amd64 version.
Ever since, the image(s) have been broken for armv7 and arm64.
As dumb-init doesn't provide 32b arm binary and because it's such a simple/small code,
this fix compiles it in a builder shallow image ; ensuring we're getting an appropriate
binary for the target arch.
We are also statically linking against musl-C as this is supported by dumb-init and is
much smaller than glibc.
- added a new generic kiwix/kiwix-tools image
- kiwix/kiwix-serve now based on kiwix/kiwix-tools ; with its entrypoint
- both images are built with official binary distribution
- both images are built on github action and pushed to both docker.io and ghcr.io
- both images are multi-arch and support arm/v7, arm64 and amd64
- built on release published or workflow_dispatch event (to be triggered by kiwix-build)
