image and standalone target

[tonistiigi]

This binary should be usable without being invoked by docker as well. The image target should be runnable with docker run.

Eg.
docker run docker/buildx build -o type=oci,dest=- git://... > oci.tgz

For auth/local sources mounts would need to be used.

Depends on adding a new driver.

[AkihiroSuda]

how it will talk to BuildKit daemon? Is it expected to be running as another container in the same netns or --network? Or buildx spawns daemon in its own container?

[tonistiigi]

buildx can have many drivers for spawning the daemon(see #10) . So in-container it can use the driver/config that spawns a daemon locally into the same container or when user runs -v /var/run/docker.sock:/var/run/docker.sock it can spawn a new container with docker driver.