dh: When there's an -indep override target without -arch, or vice versa, avoid acting...

dh: When there's an -indep override target without -arch, or vice versa, avoid acting on packages covered by the override target when running the command for packages not covered by it. Closes: #676462

Hmm, this is technically a behavior change, but hopefully not one anything
could sanely depend on working like it used to.