With the release of 11.0.2, the old URLs no longer work. This exposed a
few small bugs in the gradle config. One was that --no-cache was not
present in the docker build command, so it was not failing at
first. Then once only the ext.expansions was changed and the docker
build task was not, it was not executing it.
This commit introduces the building of the Docker images as bonafide
packaging formats alongside our existing archive and packaging
distributions. This build is migrated from a dedicated repository, and
converted to Gradle in the process.
