Comment 9 for bug 633673

It should be possible, but it would take patching koji too I think, since koji writes out the mock config files.

Panu, can you come up with any scenario where isa in BuildRequires is actually useful? I'm having a hard time coming up with one. Unlike the other macros in srpms that are arch dependent, most of those don't wind up in BuildRequires, which is the one thing we really care about in srpms (and spec files).