Checklist

• I've looked through the issues and pull requests for similar request
• This feature could be solved with a custom docker image (optional)

Describe your request

Currently, we don't use Docker in all instances (I almost entirely use podman), but to provide custom options have to define DOCKER_OPTS. Slightly more general, and namespaced, would be CROSS_CONTAINER_OPTS. For backwards compatibility, we could support both for a while, preferring the latter, then the former, and then a few releases later warn the user if they're still using DOCKER_OPTS.

Describe why this would be a good inclusion for cross

No response