Allow failure in pre-build check

.gitlab-ci.yml

@@ -45,6 +45,7 @@ pre-build-checks:
   stage: pre-build-checks
   script:
     - scripts/check-format-cpp.sh
+  allow_failure: true
 
 # Build petrack and petrack unit_tests
 build_linux:

.gitlab/merge_request_templates/merge_request.md

@@ -3,6 +3,9 @@
 
 # Reviewer Checklist
 
+## Formatting
+- [ ] the pre-build checks succeed 
+
 ## General code quality
 - [ ] naming conventions are met (see .clang-tidy for detailed information)
 - [ ] no static analyzer warnings in new code parts (e.g., use clang-tidy for checking)