Master broken / CI Strategy

One of the last commits broke the repository, i.e. I'd get compile errors on at least two locations. @ckochendoerfer tried to fix it (see https://gitlab.eclipse.org/eclipse/simopenpass/scenario_api/-/merge_requests/19 and https://gitlab.eclipse.org/eclipse/simopenpass/scenario_api/-/merge_requests/17), but we need the CI to check before merges.

@rbiegel/@adascri: can we use the simopenpass CI for this project too? @jtschea: Please update the cmake files, so we could trigger the existing tests.