[REQUEST] Support DOCKER_HOST etc

[bjeanes]

Because of crippling performance issues with Docker on macOS Mojave, I use dinghy to run Docker on macOS, which essentially runs it in a VM then mounts local directories over NFS into the VM. It's hacky, but it is about a 10x performance improvement in IO-heavy projects :(.

I'm not sure if there are inherent limitations that would make this impossible, but it'd be great if I could use bk in this context. Currently, I get the following bk local run error:

docker: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?.

[mcncl]

👋 Thanks for raising the issue! We've shipped v3 which currently doesn't have a local run tool; as you've seen there are complexities around keeping it up to date. We're looking at alternatives to local run that may provide longevity and less maintenance.