Running without --privileged returns a mount error

[ondrejbudai]

$ sudo podman run --rm ghcr.io/osbuild/image-builder-cli
mount: /run/osbuild: permission denied.
       dmesg(1) may have more information after failed mount system call.

I expect the container:

• not to require --privileged for showing help
• privileged commands (build) to show a helpful error

[supakeen]

I'll consider this a bug for now; this is likely due to the things that we do in the entrypoint.

[mvo5]

We probably need to do what we do in bib and move the container setup into the go code itself so that it has context what it needs (c.f. bibs internal/setup/setup.go code)