Use sorted sets when generating headers so we can have a deterministic output.

src/Generator/Generators/CLI/CLIHeadersTemplate.cs

@@ -43,7 +43,7 @@ namespace Cxxi.Generators.CLI
             forwardRefsPrinter = new CLIForwardRefeferencePrinter(typeRefs);
             forwardRefsPrinter.Process();
 
-            var includes = new HashSet<string>();
+            var includes = new SortedSet<string>(StringComparer.InvariantCulture);
 
             foreach (var include in forwardRefsPrinter.Includes)
             {

src/Generator/Generators/CLI/CLISourcesTemplate.cs

@@ -36,7 +36,7 @@ namespace Cxxi.Generators.CLI
 
         public void GenerateForwardReferenceHeaders()
         {
-            var includes = new HashSet<string>();
+            var includes = new SortedSet<string>(StringComparer.InvariantCulture);
 
             var typeRefs = unit.TypeReferences as TypeRefsVisitor;