When mistyping an option on the mariabackup command line mariabackup does not complain about an unknown option but continues to take the backup.

Examples:
1. Type targetdir= instead of target-dir= --> mariabackup creates a directory xtrabackup_backupfiles in the current working directory and puts the backup there.

2. Type incremental-base-dir= instead of incremental-basedir= --> mariabackup will take a full backup instead

Expected behaviour: mariabackup should throw an error on each unknown option and show the mariabackup --help output and terminate with exit code not equal 0.