Build: add make rpms target and convenience script makerpms.sh
    
    make rpms and ./makerpms.sh will produce the same RPM packages. The
    advantage of makerpms.sh is that it will take care of initial
    autoreconf & configure phases as needed.
    
    rpm-build-4.13.0-1.fc24.x86_64 broke parallel build of RPMs.
    If you get error
      INTERNAL: Exiting with 1 jobserver tokens available; should be 8!
    undefine the MAKEFLAGS variable and do not specify neither -j nor -l.
    
    https://fedorahosted.org/freeipa/ticket/6418
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>