Draft: Implement our own cppcheck support
The default cppcheck support is sub-optimal for use as it adds the full include paths to the cppcheck command line, which slows down the checking significantly. Implement our own cppcheck support by running cppcheck as a separate command for all library and executable targets.
Relates to https://its.cern.ch/jira/browse/ATLINFR-5443.
Only opening this MR for archival purposes as we ended up going with the simpler solution of having a wrapper for the cppcheck executable: athena!77034 (merged)