start_runit entrypoint doesn't come over

Upon attempting to use this image you will get:

Warning Failed 9m16s (x3 over 9m29s) kubelet, ip-10-42-32-180.us-east-2.compute.internal Error: failed to start container "calico-node": Error response from daemon: OCI runtime create failed: container_linux.go:349: starting container process caused "exec: \"start_runit\": executable file not found in $PATH": unknown

this start_runit entrypoint is not copied over from the "base" image in the multi stage build.

in the public calico image it comes over with the following lines:

# Copy in the filesystem - this contains felix, calico-bgp-daemon, licenses, etc...
COPY filesystem/ /

this brings over start_runit under sbin from here: https://github.com/projectcalico/node/tree/master/filesystem/sbin

other items under "filesystem" presumably dont come over and likely will also cause issues.