Make gateway compile without tests

[elBoberido]

This PR enables the gateway compilation without enabled tests.

Pre-Review Checklist for the PR Author

1. Code is formatted with clang-format
2. Update the PR title
   • Follow the same conventions as for commit messages
   • Link to the relevant issue
3. Relevant issues are linked
4. Add sensible notes for the reviewer
5. All checks have passed
6. Assign PR to reviewer

Notes for Reviewer

Checklist for the PR Reviewer

• Commits are properly organized and messages are according to the guideline
• Code according to our coding style and naming conventions
• Unit tests have been written for new behavior
• Copyright owner are updated in the changed files
• PR title describes the changes

Post-review Checklist for the PR Author

1. All open points are addressed and tracked via issues

References

• Relates to DDS Gateway Housekeeping #5