Fix unpacking error on Windows (chmod)

Tried to use chmod on Windows where it's not allowed.

Author: genail

Assets/PatchKit Patcher/Scripts/AppData/Local/Pack1Unarchiver.cs

@@ -130,7 +130,10 @@ private void UnpackRegularFile(Pack1Meta.FileEntry file)
                             using (var fileWritter = new FileStream(destPath, FileMode.CreateNew))
                             {
                                 Streams.Copy(gzipStream, fileWritter);
-                                Chmod.SetMode(file.Mode.Substring(3), destPath);
+                                if (Platform.IsPosix())
+                                {
+                                    Chmod.SetMode(file.Mode.Substring(3), destPath);
+                                }
                             }
                         }
                     }