cppcheck: output all annotations as error on script error
cppcheck: output all annotations as error on script error

`cppcheck` has a non-zero exit code even on warnings, so to not confuse
contributors, align the annotation output with that.

kaspar030/RIOT,OlegHahm/RIOT,ant9000/RIOT,OlegHahm/RIOT,kYc0o/RIOT,miri64/RIOT,kaspar030/RIOT,miri64/RIOT,ant9000/RIOT,OlegHahm/RIOT,miri64/RIOT,ant9000/RIOT,kYc0o/RIOT,miri64/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,jasonatran/RIOT,OlegHahm/RIOT,kYc0o/RIOT,jasonatran/RIOT,ant9000/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,miri64/RIOT,ant9000/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,jasonatran/RIOT,kaspar030/RIOT,kaspar030/RIOT,kYc0o/RIOT