Don't measure wheel size with du
    
    The `du` tool estimates disk usage, so filesystem settings
    (block size, compression, holes, etc.) might change the result.
    
    Use `stat` instead for a more reproducible result.
    
    Note that I've changed 900 (KiB) to 900000 (bytes) which is in fact not correct
    (900 KiB is 921600 bytes),
    but I assumed a human-readable round number works better here.
    I've updated the comment to say kB instead of KiB.
    
    Fixes https://bugzilla.redhat.com/2143393