Thanks, @n0npax, for producing a PR implementing what I suggested.  It looks good.  However, while testing it, I ran across earlier open Issue11122 in which the same issue of building rpms on macOS is brought up. (Sorry I didn't see this earlier!)  The solution proposed there is to just unconditionally use rpmbuild as the use of rpm was for now obsolete versions.  I don't really have any experience with rpmbuild or stake in making the change.  But, rather than applying PR 10589, it looks like following through on Issue11122 would be the better approach.  Therefore, I'm going to close this issue (and PR) as a duplicate and suggest we move the discussion and perhaps generate a new PR there.