Currently we run the CI builds while building a container, in a single docker build command. This downloads all the dependencies (compilers, build tools, libraries), copies the code from the CI workspace to the container, and then run the builds inside the container.

We should consider separating this in two steps. First create a Docker image with all the dependencies, then run a container (with docker run) with that image that runs the build.

The advantage is that we might be able to cache the build images, that saves some time. We can also mount the git workspace instead of using a COPY Docker command to copy the contents (around 250MiB) into the container.

The disadvantage is that when running locally the build script would leave build-output owned by root in your workspace.