[monotouch-test] Adjust how we detect when protocols are registered.

tests/common/TestRuntime.cs

@@ -1504,6 +1504,31 @@ public static bool IsLinkAll {
 	}
 	class LinkerSentinel { }
 
+	// Determine if any assemblies were linked by checking if a few uncommon classes in corlib are still here.
+	static bool? link_any;
+#if NET
+	[UnconditionalSuppressMessage ("Trimming", "IL2026", Justification = "This property checks whether the trimmer is enabled by checking if a type survived trimming; it's thus trimmer safe in that the any behavioral difference when the trimmer is enabled is exactly what it's looking for.")]
+#endif
+	public static bool IsLinkAny {
+		get {
+			if (!link_any.HasValue) {
+				var uncommonTypes = new string [] {
+					"System.Action`14",
+					"System.DBNull",
+					"System.Diagnostics.Debugger",
+					"System.Func`15",
+				};
+				link_any = false;
+				foreach (var uncommonType in uncommonTypes) {
+					link_any = typeof (int).Assembly.GetType (uncommonType) is null;
+					if (link_any == true)
+						break;
+				}
+			}
+			return link_any.Value;
+		}
+	}
+
 	public static bool IsOptimizeAll {
 		get {
 #if OPTIMIZEALL

tests/monotouch-test/ObjCRuntime/RegistrarTest.cs

@@ -5555,7 +5555,7 @@ void AssertMemberCount (Type type)
 #if OPTIMIZEALL || NATIVEAOT
 			var expectNoMembers = true;
 #elif !__MACOS__
-			var expectNoMembers = global::XamarinTests.ObjCRuntime.Registrar.IsStaticRegistrar;
+			var expectNoMembers = global::XamarinTests.ObjCRuntime.Registrar.IsStaticRegistrar && TestRuntime.IsLinkAny;
 #else
 			var expectNoMembers = false;
 #endif