OK, interesting as all that was, I don't think we reached a conclusion:
a) can we query rpm inside a spec or not?
b) If no to (a) can we go about ascertaining the build time emacs
version reliably some other way.
c) If no to (b), is it acceptable to have packagers putting the
Requires: emacs >= N.n.nn in themselves?
[In the past, I've always done c].