Add graphviz install trigger
    
    graphviz utilitizes a plugin cache which needs to be created once
    installed.  While graphviz does have its own %post to do so, when built
    in /app it does not work because it first requires ldconfig to be run
    (so that the plugins can resolve graphviz's own libraries).
    
    graphviz's %post has been converted to a trigger in rawhide (F40), but
    in the meantime for F39, this avoids the issue.