Fix the use of obsolete wxDD_NEW_DIR_BUTTON in wxOSX.

Use wxDD_DIR_MUST_EXIST, testing for wxDD_NEW_DIR_BUTTON always failed.

Closes #13596.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@72815 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/osx/cocoa/dirdlg.mm

@@ -65,7 +65,7 @@ WX_NSOpenPanel wxDirDialog::OSXCreatePanel() const
     wxCFStringRef cf( m_message );
     [oPanel setMessage:cf.AsNSString()];
 
-    if ( HasFlag(wxDD_NEW_DIR_BUTTON) )
+    if ( !HasFlag(wxDD_DIR_MUST_EXIST) )
         [oPanel setCanCreateDirectories:YES];
 
     return oPanel;