[msbuild] Copy the entire frameworks to the Mac when building remotely in the ResolveNativeReferences task. Fixes #19173. (#19227)

Fixes https://github.com/xamarin/xamarin-macios/issues/19173.

msbuild/Xamarin.MacDev.Tasks/Tasks/ResolveNativeReferencesBase.cs

@@ -524,6 +524,9 @@ namespace Xamarin.MacDev.Tasks {
 			return false;
 		}
 
-		public IEnumerable<ITaskItem> GetAdditionalItemsToBeCopied () => Enumerable.Empty<ITaskItem> ();
+		public IEnumerable<ITaskItem> GetAdditionalItemsToBeCopied ()
+		{
+			return CreateItemsForAllFilesRecursively (NativeReferences);
+		}
 	}
 }

msbuild/Xamarin.MacDev.Tasks/Tasks/XamarinTask.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
+using System.Linq;
 
 using Microsoft.Build.Framework;
 using Microsoft.Build.Tasks;
@@ -217,5 +219,25 @@ namespace Xamarin.MacDev.Tasks {
 			foundInMetadata = false;
 			return fallbackValue;
 		}
+
+		protected IEnumerable<ITaskItem> CreateItemsForAllFilesRecursively (IEnumerable<string>? directories)
+		{
+			if (directories is null)
+				yield break;
+
+			foreach (var dir in directories) {
+				// Don't try to find files if we don't have a directory in the first place (or it doesn't exist).
+				if (!Directory.Exists (dir))
+					continue;
+
+				foreach (var file in Directory.EnumerateFiles (dir, "*", SearchOption.AllDirectories))
+					yield return new TaskItem (file);
+			}
+		}
+
+		protected IEnumerable<ITaskItem> CreateItemsForAllFilesRecursively (IEnumerable<ITaskItem>? directories)
+		{
+			return CreateItemsForAllFilesRecursively (directories?.Select (v => v.ItemSpec));
+		}
 	}
 }