[monotouch-test] Fix bool encoding in tests on X64 on Mac Catalyst.

    [FAIL] TestTypeEncodings :   xamarin#14
      String lengths are both 1. Strings differ at index 0.
      Expected: "B"
      But was:  "c"
      -----------^

Hopefully this is right?

Ref: d6d02fa

src/ObjCRuntime/Registrar.cs

@@ -2655,7 +2655,7 @@ protected string ToSignature (TType type, ObjCMember member, ref bool success, b
 			case "System.Double": return "d";
 			case "System.Boolean":
 				// map managed 'bool' to ObjC BOOL = 'unsigned char' in OSX and 32bit iOS architectures and 'bool' in 64bit iOS architectures
-#if MONOMAC
+#if MONOMAC || __MACCATALYST__
 				return IsARM64 ? "B" : "c";
 #else
 				return Is64Bits ? "B" : "c";

tests/monotouch-test/ObjCRuntime/RegistrarTest.cs

@@ -1450,10 +1450,8 @@ public void TestTypeEncodings ()
 		{
 			var cl = new Class (typeof (TestTypeEncodingsClass));
 			var sig = Runtime.GetNSObject<NSMethodSignature> (Messaging.IntPtr_objc_msgSend_IntPtr (cl.Handle, Selector.GetHandle ("methodSignatureForSelector:"), Selector.GetHandle ("foo::::::::::::::::")));
-#if MONOMAC
+#if MONOMAC || __MACCATALYST__
 			var boolEncoding = TrampolineTest.IsArm64CallingConvention ? "B" : "c";
-#elif __MACCATALYST__
-			var boolEncoding = "B";
 #else
 			var boolEncoding = (IntPtr.Size == 8 || TrampolineTest.IsArmv7k || TrampolineTest.IsArm64CallingConvention) ? "B" : "c";