[xharness] Don't try to run 32-bit tests on devices that don't support 32-bits. (#2749)

tests/xharness/Jenkins.cs

@@ -168,7 +168,7 @@ namespace xharness
 						Platform = TestPlatform.iOS_Unified32,
 						TestName = project.Name,
 					};
-					rv.Add (new RunDeviceTask (build32, Devices.ConnectedDevices.Where ((dev) => dev.DevicePlatform == DevicePlatform.iOS)) { Ignored = ignored || !IncludeiOS });
+					rv.Add (new RunDeviceTask (build32, Devices.ConnectedDevices.Where ((dev) => dev.DevicePlatform == DevicePlatform.iOS && dev.Supports32Bit)) { Ignored = ignored || !IncludeiOS });
 
 					var todayProject = project.AsTodayExtensionProject ();
 					var buildToday = new XBuildTask {

tests/xharness/Simulators.cs

@@ -619,6 +619,21 @@ namespace xharness
 			get { return Architecture == Architecture.ARM64; }
 		}
 
+		public bool Supports32Bit {
+			get {
+				switch (DevicePlatform) {
+				case DevicePlatform.iOS:
+					return Version.Parse (ProductVersion).Major < 11;
+				case DevicePlatform.tvOS:
+					return false;
+				case DevicePlatform.watchOS:
+					return true;
+				default:
+					throw new NotImplementedException ();
+				}
+			}
+		}
+
 		public Architecture Architecture {
 			get {
 				var model = ProductType;