[CarPlay] Add Support for DotNet Attributes

Co-authored-by: TJ Lambert <tjlambert@microsoft.com>

src/CarPlay/CPCompat.cs

@@ -11,12 +11,18 @@ using System;
 using Foundation;
 using ObjCRuntime;
 using System.ComponentModel;
+using System.Runtime.Versioning;
 
 #if !XAMCORE_4_0
 namespace CarPlay {
 	[Register (SkipRegistration = true)]
+#if !NET
 	[Unavailable (PlatformName.iOS, PlatformArchitecture.All)]
 	[Obsolete ("This API has been removed from the native SDK.")]
+#else
+	[UnsupportedOSPlatform ("ios")]
+	[Obsolete ("This API has been removed from the native SDK.", DiagnosticId = "BI1234", UrlFormat = "https://github.com/xamarin/xamarin-macios/wiki/Obsolete")]
+#endif
 	[EditorBrowsable (EditorBrowsableState.Never)]
 	public class CPEntity : NSObject, INSSecureCoding {