fix 5466: explicity including a file causes a build break (#5475)

* fix 5466: explicity including a file causes a build break

* fix failing unit tests

* Add unit tests and apply fix also to includeFiles

* apply review feedback

TestAssets/TestProjects/TestAppWithExplicitInclude/Program.cs

@@ -0,0 +1,9 @@
+using System;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Hello World!");
+    }
+}