Replace kubernetes build pod with plain podman container

Currently, the build/compilation container is a Kubernetes pod. There are two problems with this:

• You need to have set up minikube or a cluster to compile CTA
• The repo needs to be in a very specific place /home/cirunner/shared/CTA

Neither of these are ideal, so we should change this to a simple podman/docker setup, meaning that you can also compile easily on a local machine without access to minikube (although you won't be able to run the tests of course)