Make the CPP ABI visible only to the STD symbols

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Passes/SymbolsCodeGenerator.cs

@@ -27,13 +27,14 @@ namespace CppSharp.Passes
         }
 
         public override void Process()
+        {
+            if (TranslationUnit.Module == Options.SystemModule)
             {
                 WriteLine("#define _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS");
                 WriteLine("#define _LIBCPP_HIDE_FROM_ABI");
                 NewLine();
-
-            if (TranslationUnit.Module == Options.SystemModule)
                 WriteLine("#include <string>");
+            }
             else
                 foreach (var header in TranslationUnit.Module.Headers)
                     WriteLine($"#include <{header}>");