fix backcompat on unix for config brkn in 7a7a72f

Only load config files with the app name set to "visualboyadvance-m" on
Windows and Mac, on unix keep the default of "vbam" for now so that
users' ~/.vbam directories are found correctly.

TODO:

* migrate all of this properly to XDG paths on unix, giving users the
  option to move their config

src/wx/wxvbam.cpp

@@ -53,7 +53,11 @@ static void get_config_path(wxPathList& path, bool exists = true)
 {
     // we want paths with "visualboyadvance-m" not "vbam", so change appname temporarily
     wxString current_app_name = wxGetApp().GetAppName();
+
+    // keep config path as ~/.vbam on UNIX for now for backcompat
+#if defined(__WXMSW__) || defined(__WXMAC__)
     wxGetApp().SetAppName(_("visualboyadvance-m"));
+#endif
 
     //   local config dir first, then global
     //   locale-specific res first, then main