Fixed typo in Options.cs added in 6855901ca6.

Closes https://github.com/mono/CppSharp/issues/649.

src/Generator/Options.cs

@@ -70,7 +70,7 @@ namespace CppSharp
         public bool IsMicrosoftAbi { get { return Abi == CppAbi.Microsoft; } }
 
         // Library options
-        public List<string> Libraries { get { return Module.Headers; } }
+        public List<string> Libraries { get { return Module.Libraries; } }
         public bool CheckSymbols;
 
         public string SharedLibraryName