See https://github.com/openshift/source-to-image/blob/01312890680b03966cc8915286aaae36bbb34961/docs/runtime_image.md

The runtime images will need (at least)

• the label io.openshift.s2i.scripts-url
• a script /usr/local/s2i/assemble-runtime

Success criteria:

• A user can invoke an S2I-with-runtime build process (via OpenShift, or the s2i standalone binary), specifying an OpenJDK container runtime image as the runtime image to use, the process completes successfully and produces an application runtime image that can be started.