S. Riette Sept 23: add --computeRefIfNeeded and --onlyIfNeeded switches to check_commit_testprogs

        --onlyIfNeeded allows to call check_commit_ial and compuation (pack creation,
                       compilation, execution) are performed only if needed

        --computeRefIfNeeded with this switch, if the reference simulation does not
                             exist, this reference simulation is built before
                             performing the comparison