Macroize build root policies for consistent disable/override ability
    
    Add a separate macro for each brp we have, using standard naming
    convention and conditionalize the usage in %__os_install_post.
    Voilà, we have a standard way to disable (and also override) any brp
    scripts from specs that need it and a common scheme for new brps
    to follow.
    
    Note that this is not supposed to change the existing behavior and
    default build root policy invocations at all, any change in those
    would be a thinko/typo/copy-paste error in this commit.
    
    (cherry picked from commit c4646d791dea6b976fd5a04e2562c7b21b9389e0)
    Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>