The config/certs directory of Elasticsearch is not readable by other
users and groups. This work in the public image, which uses the root
user, but the Wolfi image does not. Using the same user id fixes the
problem.
* Fix Docker image build on Linux
* Build Docker images in CI
* Fix bash syntax
* Only load, not push
* Parallelize docker build
It's currently the slowest step.
* Only build Linux images
