Fix a build error on Xcode 16

Author: scenee

Sources/SurfaceView.swift

@@ -45,11 +45,13 @@ public class SurfaceAppearance: NSObject {
         }
     }()
 
+    #if swift(>=6.2)
     @available(iOS 26.0, *)
     public var cornerConfiguration: UICornerConfiguration? {
         get { _cornerConfiguration as? UICornerConfiguration }
         set { _cornerConfiguration = newValue }
     }
+    #endif
 
     private var _cornerConfiguration: Any?
 
@@ -384,11 +386,13 @@ public class SurfaceView: UIView {
     }
 
     private func updateCornerRadius() {
+        #if swift(>=6.2)
         if #available(iOS 26.0, *), let cornerConfiguration = appearance.cornerConfiguration {
             containerView.cornerConfiguration = cornerConfiguration
             containerView.layer.masksToBounds = true
             return
         }
+        #endif
         containerView.layer.cornerRadius = appearance.cornerRadius
         guard containerView.layer.cornerRadius != 0.0 else {
             containerView.layer.masksToBounds = false