Fix compilation issues when building SwiftUI Previews for macOS. (#376)

Author: Zandor300

Source/Device.generated.swift

@@ -11,8 +11,10 @@
 
 #if os(watchOS)
 import WatchKit
-#else
+#elseif canImport(UIKit)
 import UIKit
+#else
+import Foundation
 #endif
 
 // MARK: Device

Source/Device.swift.gyb

@@ -299,8 +299,10 @@ watchOSDevices = watches
 }%
 #if os(watchOS)
 import WatchKit
-#else
+#elseif canImport(UIKit)
 import UIKit
+#else
+import Foundation
 #endif
 
 // MARK: Device