Starting with Xcode 4.5 the possibility of building for armv6 devices is not given anymore (iPhone/iPod touch 1st and 2nd generation). This means no new versions of our app for
Yes, there are workarounds. If you need to actually take advantage of new iOS 6 features, try either of the first couple answers to this related question. The first answer requires using both Xcode 4.4 and 4.5. If you never want to have to open Xcode 4.4, then use the second answer.
If you just want to be able to build an executable in Xcode 4.5 that works on armv6, armv7 and armv7s devices, without actually taking advantage of new iOS 6 SDK APIs, then you can see my answer to another question, which is much simpler ... but has the limitation that you can't take advantage of new iOS 6 features on iOS 6 devices.