Fix WSL InvariantCulture test.

SelfContained/Program.cs

@@ -16,7 +16,7 @@ public static class Program
 
         #region The code in this region is not intended for use in a self-contained single-file. It's just here to make sure there is no functionality break with localization in Terminal.Gui using single-file
 
-        if (Equals (Thread.CurrentThread.CurrentUICulture, CultureInfo.InvariantCulture))
+        if (Equals (Thread.CurrentThread.CurrentUICulture, CultureInfo.InvariantCulture) && Application.SupportedCultures.Count == 0)
         {
             Debug.Assert (Application.SupportedCultures.Count == 0);
         }