GeminiProtocl: Fix attribution not being set, and not compiling on macOS

GeminiProtocol/GeminiDataTask.swift

@@ -19,6 +19,7 @@ public class GeminiDataTask {
     private let connection: NWConnection
     // todo: remove stupid hack when deployment target is >= iOS 15/macOS 12
     private var _attribution: Any? = nil
+    #if os(iOS)
     @available(iOS 15.0, *)
     public var attribution: NWParameters.Attribution {
         get {
@@ -28,6 +29,7 @@ public class GeminiDataTask {
             _attribution = newValue
         }
     }
+    #endif
     
     public init(request: GeminiRequest, completion: @escaping Completion) {
         self.request = request
@@ -36,10 +38,6 @@ public class GeminiDataTask {
         let endpoint: NWEndpoint = .hostPort(host: NWEndpoint.Host(request.url.host!), port: NWEndpoint.Port(rawValue: port)!)
         self.connection = NWConnection(to: endpoint, using: .gemini)
         
-        if #available(iOS 15.0, *) {
-            connection.parameters.attribution = attribution
-        }
-        
         self.connection.stateUpdateHandler = { (newState) in
             switch newState {
             case .ready:
@@ -65,6 +63,13 @@ public class GeminiDataTask {
     
     public func resume() {
         guard state == .unstarted else { return }
+        
+        #if os(iOS)
+        if #available(iOS 15.0, *) {
+            connection.parameters.attribution = attribution
+        }
+        #endif
+        
         state = .started
         connection.start(queue: GeminiDataTask.queue)
     }