This optimizes our image in a few different ways:
- It adds a bunch of files and directories to the `.dockerignore` file.
This lets us have a single `COPY . .` but still be very aggressive about pruning what files end up in the build context.
- It adds build-time cache mounts to the `go build` commands using BuildKit's `--mount=type=cache` flag.
This requires BuildKit-capable Docker, but means that our Go builds can all be incremental builds.
This replaces the previous flow we had where we needed to split out `go mod download`.
- Instead of letting the full `apt-get install ca-certificates` layer end up in our final image, we copy just the single file we need.
Signed-off-by: Matt Moyer <moyerm@vmware.com>
