rpmdev-bumpspec is only used in the top level Makefile if you are doing 'make debug' or 'make relese'.  Neither of those are run during the RPM build itself.  The current rawhide kernel has this addition in the makefile, but rpmdevtools isn't included in the buildroot at all.

I don't think a BR is actually needed, unless you are seeing something I'm not.

I cloned the Fedora kernel git tree, then did these commands:

$ make nodebug nodebuginfo

At that point, it complains about a missing rpmdev-bumpspec. You are right, however, that I did not verify whether or not the kernel would still build without the spec having been bumped :)

(In reply to comment #2)
> I cloned the Fedora kernel git tree, then did these commands:
> 
> $ make nodebug nodebuginfo

Right, that's never run during the RPM build.

> At that point, it complains about a missing rpmdev-bumpspec. You are right,
> however, that I did not verify whether or not the kernel would still build
> without the spec having been bumped :)

We could still add a BR for it, but that isn't even going to solve the problem you hit because we aren't even doing anything with RPM at that point.

I think we'll close this bug out now given the conversation above.