Build: enable silent build in makerpms.sh
    
    Build called from makerpms.sh is not verbose by default anymore.
    It still prints all directories and files it builds but the long
    command lines are hidden by default.
    
    It has the advantage that compiler and other warnings are visible to
    developers right away. If you need to debug something,
    use --disable-silent-rules to override the default
    (or call configure manually).
    
    https://fedorahosted.org/freeipa/ticket/6418
    
    Reviewed-By: Lukas Slebodnik <lslebodn@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>