I have an Xcode project which holds different versions of my game: iOS (iPhone and iPad) and OS X.
I have a different target for each device, platform. Every application works fine, on simulator, devices, etc. I even have some builds currently in the iOS AppStore.
My problem is with the OS X build, which runs just fine when launched from Xcode, but with this forbidden icon on top of the regular app icon.

The problem, is when I try to export/archive this build, the exported application still has this forbidden mark. And when I launch it from the Finder, I get the following message.
You can’t open the application “Foo bar” because it is not supported on this type of Mac.
I did try to run the following command:
file Contents/MacOS/Foobar
Which outputs:
Contents/MacOS/Foobar: Mach-O 64-bit executable x86_64
I would think it should run just fine on my Macbook Air, plus it runs well when launched from Xcode debug command.
Anyone has an idea?
Thanks,
I had forgotten to remove this settings from my OS X Info.plist file:
Thanks Michelle for the great help! The flag lead me to the solution.