fix compilation after last change for compilers without variadic macros support

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42990 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/x11/clipbrd.cpp

@@ -32,11 +32,14 @@ Atom  g_clipboardAtom   = 0;
 Atom  g_targetsAtom     = 0;
 #endif
 
-#ifdef __WXDEBUG__
+// avoid warnings about unused static variable
+#if defined(__WXDEBUG__) && defined(HAVE_VARIADIC_MACROS)
+
 // the trace mask we use with wxLogTrace() - call
 // wxLog::AddTraceMask(TRACE_CLIPBOARD) to enable the trace messages from here
 // (there will be a *lot* of them!)
 static const wxChar *TRACE_CLIPBOARD = _T("clipboard");
+
 #endif // __WXDEBUG__
 
 //-----------------------------------------------------------------------------