This will use the Appsmith base image which contains all the downloads
needed, so the image build in daily CI should be much more reliable, and
quite likely much faster.
All workflows have already been updated to use the BASE build argument
to set the base image.
Once this is merged, building the Docker image will fail if `BASE` build
argument is not passed. This is that the base is set explicitly
everywhere to not cause any confusion.
The deleted content has been moved to
8d34a2ac28/deploy/docker/base.dockerfile,
which builds the `base-*:*` images.
The layers in the Dockerfile that depend on downloading large files from
external sources, doesn't have to run every day, or at every PR. We
tried using Docker's caching configuration, but it's not as reliable as
we'd have liked.
A separate base image lends us much more control over the how long we
cache the downloaded files and how often we redo this.
This PR only _adds_ the base image. It doesn't change anything in the
build of the existing Docker image. That'll happen once we have the base
images for `release` and `master` already present on DockerHub.
