Use specific Dockerfile per image and architecture

[LKHN]

The init and micro images need different Docker files than default and minimal. reference for init:

• 2.4. Understanding the UBI init images
• Running systemd in a non-privileged container Blog I think it may give us the flexibility for image/architecture-specific metadata and other changes. Example: https://github.com/LKHN/docker-images/tree/buildsh-dockerfile

[srbala]

@LKHN doing some udpate to build.sh, we can manage without creating Dockerfile. Script has TYPE has necessary to process it

OLD Generation step

cat << EOF > "${OUTPUT_DIR}/Dockerfile"
FROM scratch
ADD ${IMAGE_NAME} /
CMD ["/bin/bash"]
EOF

Proposed

STARTCMD=$( cat <<EOF

CMD ["/bin/bash"]
EOF
)

if [ ${TYPE} == 'init' ]; then
  STARTCMD=$( cat <<EOF

CMD ["/bin/init"]

STOPSIGNAL SIGRTMIN+3
EOF
)
fi

if [ ${TYPE} == 'micro' ]; then
  STARTCMD=$( cat <<EOF

CMD ["/bin/sh"]
EOF
)
fi

cat << EOF > "${OUTPUT_DIR}/Dockerfile"
FROM scratch
ADD ${IMAGE_NAME} /
${STARTCMD}
EOF