try to silence C compiler warning about unused function argument

Cython/Compiler/ModuleNode.py

@@ -702,7 +702,7 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
         PyrexTypes.c_int_type.create_from_py_utility_code(env)
 
         code.put(Nodes.branch_prediction_macros)
-        code.putln('static CYTHON_INLINE void __Pyx_pretend_to_initialize(void* ptr) {}')
+        code.putln('static CYTHON_INLINE void __Pyx_pretend_to_initialize(void* ptr) { (void)ptr; }')
         code.putln('')
         code.putln('static PyObject *%s;' % env.module_cname)
         code.putln('static PyObject *%s;' % env.module_dict_cname)