Warning fixes.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@28229 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/utilscmn.cpp

@@ -505,7 +505,10 @@ static long wxDoExecuteWithCapture(const wxString& command,
         }
 
     }
-#endif // wxUSE_STREAMS
+#else
+    wxUnusedVar(output);
+    wxUnusedVar(error);
+#endif // wxUSE_STREAMS/!wxUSE_STREAMS
 
     delete process;