Add %bcond for minizip and do some cleanup
    
    We should drop the minizip subpackage one day since that's totally
    unsupported upstream, have a look e.g. at [1].  Nowadays there are
    forks like [2] that could replace subpackage.  I contacted both
    original minizip authors (per zlib upstream), and both redirected
    me to [2].
    
    [1] https://github.com/madler/zlib/pulls/praiskup
    [2] https://github.com/nmoinvaz/minizip
    
    Related: rhbz#1609830
    Version: 1.2.11-10