xcassets: A XXxXX app icon is required for iPhone apps targeting releases of iOS prior to 7.0

When trying to handle all icons and images using xcassets I get warnings stating that 57x57, 57x57@2x, 72x72 and 72x72@2x icons are needed as I target iOS 5+ devices.

The problem is that:

The default AppIcon group won't accept those icons.
Adding separate entries for Icon and Icon-72 won't fix the warnings neither.

Solution

Solved it by right clicking and choosing Editor > New App Icon. This created a new AppIcon group with both iOS 6 and 7 icon placeholders.

The problem was due to Xcode templates where all new projects are iOS 7+ by default.

Also configurable by selecting the AppIcon image set and using the Attributes Inspector:

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