WL4189 Cap the autodetected parallelism value to 8

    for my $limit (2000, 1500, 1000, 500){

      $opt_parallel-- if ($sys_info->min_bogomips() < $limit);

    }

    $opt_parallel= 8 if ($opt_parallel > 8);

    $opt_parallel= $num_tests if ($opt_parallel > $num_tests);

    $opt_parallel= 1 if ($opt_parallel < 1);

    mtr_report("Using parallel: $opt_parallel");