Commit 691c8f68283f34aa2d486a29c08b5d683f0675aa broke the cppcheck job
in GitLab CI: when cppcheck fails, the script is immediately
interrupted, preventing cppcheck-htmlreport from being run. To ensure
the HTML report is generated when cppcheck fails, revert to invoking
cppcheck-htmlreport in the "after_script" part of the job.