title: Swift Package minimum ios version
body: <p>I've created my package which I would like to use in my projects. In the package, I'm using UIStackView. When I adding the package to the project and running it I get errors <strong>'UIStackView' is only available in iOS 9.0 or newer</strong>. 
  Why I get this error if my project iOS target sitting set to 9.0? How can I solve this problem without making iOS 8 support in the package?</p>