Add submodule step to CI

.gitlab-ci.yml

@@ -26,6 +26,7 @@ build-job:       # This job runs in the build stage, which runs first.
   stage: build
   image: $CI_REGISTRY/daphne4nfdi/sassena:latest
   script:
+    - git submodule update --init --recursive
     - cmake --preset=ci .
     - cd build-ci
     - ninja -j3