[msbuild] Verify Mac Catalyst apps like we verify macOS apps. Fixes #17829. (#17835)

* For Mac Catalyst apps we must verify the code signature like we do it for macOS apps. Fixes #17829.
* Enable nullability and fix code accordingly.
* Merge the CodesignVerify and CodesignVerifyTaskBase classes to simplify the code.

Submission test is added as well:

* https://github.com/xamarin/maccore/pull/2656
* https://github.com/xamarin/SubmissionSamples/pull/51

Fixes https://github.com/xamarin/xamarin-macios/issues/17829.

msbuild/Xamarin.MacDev.Tasks/Tasks/CodesignVerify.cs

@@ -1,21 +0,0 @@
-using Xamarin.Messaging.Build.Client;
-
-namespace Xamarin.MacDev.Tasks {
-	public class CodesignVerify : CodesignVerifyTaskBase {
-		public override bool Execute ()
-		{
-			if (ShouldExecuteRemotely ())
-				return new TaskRunner (SessionId, BuildEngine4).RunAsync (this).Result;
-
-			return base.Execute ();
-		}
-
-		public override void Cancel ()
-		{
-			if (ShouldExecuteRemotely ())
-				BuildConnection.CancelAsync (BuildEngine4).Wait ();
-
-			base.Cancel ();
-		}
-	}
-}

msbuild/Xamarin.MacDev.Tasks/Tasks/CodesignVerifyTaskBase.cs

@@ -4,17 +4,20 @@ using System.IO;
 using Microsoft.Build.Framework;
 
 using Xamarin.Localization.MSBuild;
+using Xamarin.Messaging.Build.Client;
 using Xamarin.Utils;
 
+#nullable enable
+
 namespace Xamarin.MacDev.Tasks {
-	public abstract class CodesignVerifyTaskBase : XamarinToolTask {
+	public class CodesignVerify : XamarinToolTask {
 		#region Inputs
 
 		[Required]
-		public string CodesignAllocate { get; set; }
+		public string CodesignAllocate { get; set; } = string.Empty;
 
 		[Required]
-		public string Resource { get; set; }
+		public string Resource { get; set; } = string.Empty;
 
 		#endregion
 
@@ -43,9 +46,9 @@ namespace Xamarin.MacDev.Tasks {
 			case ApplePlatform.iOS:
 			case ApplePlatform.TVOS:
 			case ApplePlatform.WatchOS:
-			case ApplePlatform.MacCatalyst:
 				args.AddQuoted ("-R=anchor apple generic and certificate 1[field.1.2.840.113635.100.6.2.1] exists and (certificate leaf[field.1.2.840.113635.100.6.1.2] exists or certificate leaf[field.1.2.840.113635.100.6.1.4] exists)");
 				break;
+			case ApplePlatform.MacCatalyst:
 			case ApplePlatform.MacOSX:
 				args.Add ("--deep");
 				break;
@@ -66,11 +69,22 @@ namespace Xamarin.MacDev.Tasks {
 
 		public override bool Execute ()
 		{
+			if (ShouldExecuteRemotely ())
+				return new TaskRunner (SessionId, BuildEngine4).RunAsync (this).Result;
+
 			EnvironmentVariables = new string [] {
 				"CODESIGN_ALLOCATE=" + CodesignAllocate
 			};
 
 			return base.Execute ();
 		}
+
+		public override void Cancel ()
+		{
+			if (ShouldExecuteRemotely ())
+				BuildConnection.CancelAsync (BuildEngine4).Wait ();
+
+			base.Cancel ();
+		}
 	}
 }

msbuild/Xamarin.Shared/Xamarin.Shared.targets

@@ -1959,7 +1959,7 @@ Copyright (C) 2018 Microsoft. All rights reserved.
 	-->
 	<Target
 		Name="_CodesignVerify"
-		Condition="'$(_CodesignAppBundleCondition)' == 'true' And '$(_RequireCodeSigning)' == 'true'"
+		Condition="'$(_CodesignAppBundleCondition)' == 'true' And '$(_RequireCodeSigning)' == 'true' And '$(DisableCodesignVerification)' != 'true'"
 		DependsOnTargets="_CodesignAppBundle"
 		>
 		<CodesignVerify