Ensure rust2rpm doesn't autogenerate architecture-dependent patches
    
    The logic in the cfg-expression evaluator checked *too many cases*,
    some of which would have resulted in generation of broken patches
    and packages. We need to ensure that the evaluation is independent
    of the host architecture (i.e. we need to keep *all* dependencies
    that are valid on *any* of our build targets, even if they end up
    being unused on *some* of them).