Refactor Dockerfile to produce a single layer image

# syntax = docker/dockerfile:1.0-experimental

FROM debian:buster-slim as collect

COPY LICENCE.txt /stage/LICENCE.txt

COPY collect-binaries.bash /bin/collect-binaries

COPY collect-binaries.bash /stage/scripts/collect-binaries

COPY config-nsswitch.bash /stage/scripts/config-nsswitch

RUN collect-binaries /bin/bash

FROM scratch

ENV PATH=/scripts:/bin

COPY LICENCE.txt /LICENCE.txt

COPY --from=collect /stage /

COPY collect-binaries.bash /scripts/collect-binaries

COPY config-nsswitch.bash /scripts/config-nsswitch

ENTRYPOINT ["/bin/bash"]