use wxMac provided wxGetOsDescription with Apple DevTools

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@13705 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/unix/utilsunx.cpp

@@ -948,6 +948,7 @@ bool wxGetUserName(wxChar *buf, int sz)
     return FALSE;
 }
 
+#ifndef __WXMAC__
 wxString wxGetOsDescription()
 {
 #ifndef WXWIN_OS_DESCRIPTION
@@ -956,6 +957,7 @@ wxString wxGetOsDescription()
     return WXWIN_OS_DESCRIPTION;
 #endif
 }
+#endif
 
 // this function returns the GUI toolkit version in GUI programs, but OS
 // version in non-GUI ones