title: Xcode error when Package.swift platform changed from v13 to v14 "v14 unavailable"
body: <p>I need features in iOS v14. I have a local package. When I change the platforms item in &quot;Packages.swift&quot;,</p>
  <p>platforms: [.macOS(.v10_15), .iOS(.v14)],</p>
  <p>I get the error 'v14' unavailable.</p>
  <p>The app deployment target is set to 14.1.
  I'm running Xcode v12.5.1</p>