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
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.