[CI] Make sure all pacxx-repositories have a decent CI setup

Repositories:

• https://gitlab.dune-project.org/joe/pacxx-docker
  • Style
  • Trigger rebuild (N/A)
  • cuda
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx
  • Style
  • Trigger rebuild
  • cuda
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-runtime
  • Style
  • Trigger rebuild
  • cuda
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-samples
  • Style
  • Trigger rebuild
  • cuda
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-llvm2
  • Style
  • Trigger rebuild
  • cuda
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-rv2
  • Style
  • Trigger rebuild
  • cuda
• https://zivgitlab.uni-muenster.de/HPC2SE-Project/pacxx-clang
  • Style
  • Trigger rebuild
  • cuda

Decent means:

• Testing with cuda
• Trigger docker rebuild, where applicable
• Adheres to a common .gitlab-ci.yml style with as little deviations as necessary