Can't build out to iOs10 from Unity 5.4.1

Struggling to build to iOS10 with Xcode8. Error suggests Unity 5.4.1 is building a file too old for the deployment target. Any suggestions would be massively appreciated.
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Thanks @hexagonius - this is the error80643-screen-shot-2016-10-21-at-181716.png

Then we selected Main.storyboard in the project navigator, pressed ⌘⌥1 to show the Identity Inspector and changed Builds for for something suitable but just got this - there was not iOS10 option to select.

Tried building out using an old version of Xcode - no joy. The only luck we’ve had is building out a version of the project that was built using an older version of Unity (3.5.3)