[xtro] Append the lines and then sort them to get everything grouped better. (#12274)

tests/xtro-sharpie/Makefile

@@ -194,3 +194,6 @@ remove-empty-files:
 unclassified2todo:
 	$(SYSTEM_CSC) -features:strict Filter.cs u2todo/u2todo.cs
 	$(MONO) u2todo.exe
+	@for filename in $(git status -s | cut -c4- | grep .todo); do \
+		sort -o "$filename" "$filename"; \
+	done

tests/xtro-sharpie/u2todo/u2todo.cs

@@ -17,7 +17,7 @@ class Program {
 			var todo = Path.ChangeExtension (file, ".todo");
 			if (File.Exists (todo)) {
 				Console.WriteLine ($"Appending {file} to {todo}");
-				var content = "## appended from unclassified file" + Environment.NewLine + File.ReadAllText (file);
+				var content = File.ReadAllText (file);
 				File.AppendAllText (todo, content);
 				File.Delete (file);
 			} else {