[FEATURE] Make it possible to use podman instead of docker

[chrysophylax]

Is your feature request related to a problem? Please describe.
We use the podman family for all our container-based workflows. Currently, the build scripts error out on docker being missing whenever we invoke bb hl:compile.

I have set $DOCKER_HOST to the podman unix socket

Describe the solution you'd like
Podman works!
Describe alternatives you've considered
Installing docker and having a mixed docker/podman workflow with a workaround just for holy-lambda workflows

Additional context

[billy@glorfindel ~]$ systemctl --user enable podman.socket
systemctl --user start podman.socket
systemctl --user status podman.socket
export DOCKER_HOST=unix:///run/user/$UID/podman/podman.sock
● podman.socket - Podman API Socket
     Loaded: loaded (/usr/lib/systemd/user/podman.socket; enabled; vendor prese>
     Active: active (listening) since Tue 2022-05-31 10:01:54 CEST; 3h 22min ago
      Until: Tue 2022-05-31 10:01:54 CEST; 3h 22min ago
   Triggers: ● podman.service
       Docs: man:podman-system-service(1)
     Listen: /run/user/1000/podman/podman.sock (Stream)
     CGroup: /user.slice/user-1000.slice/user@1000.service/app.slice/podman.soc>

May 31 10:01:54 glorfindel systemd[1379]: Listening on Podman API Socket.
[billy@glorfindel basic.example]$ bb hl:compile
[holy-lambda] Docker is not running! Enable and run docker first before using holy-lambda!

[kwojcik-blockether]

Thanks @chrysophylax. This is certainly a nice enchancement! I'll try to tackle the issue in the end of this week, or in the next one. All the best!