I just upgraded my MacBook OS to Yosemite and upgraded Xcode from 6.0 to 6.1, and now when I create my project and try to run for iPhone 5 with iOS7.0, it gives me the error message " iPhone 5s unavailable, select another device and try again.In Xcode 6.0 this worked fine.
Below are the build settings for my application.
Architecture - Standard Architecture(armv7, arm64) Base SDK - Latest iOS(iOS 8.1) Valid architectures - arm64, armv7, armv7s iOS Deployment Target - iOS6
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