Allow ssh socket from host or certain ssh keys to be exposed to a
certain RUN instruction, but not any other instructions, as well as not
showing up in the final image.
This is done by spawining a new agent from buildah and mounting
the listening socket inside the run. SSH_AUTH_SOCK inside the container
will be set to the socket mountpoint. The defualt mountpoint is
/run/buildkit/ssh_agent.{i}
Signed-off-by: Ashley Cui <acui@redhat.com>
Kir Kolyshkin
flouthoc
Nalin Dahyabhai
Ashley Cui