Fix build against wxWidgets older than 3.1.1

src/slic3r/GUI/ConfigWizard.cpp

@@ -819,7 +819,22 @@ void PageMaterials::update_lists(int sel_type, int sel_vendor, int last_selected
 	wxArrayInt sel_printers;
 	int sel_printers_count = list_printer->GetSelections(sel_printers);
 
-	if (sel_printers != sel_printers_prev) {
+    // Does our wxWidgets version support operator== for wxArrayInt ?
+    // https://github.com/prusa3d/PrusaSlicer/issues/5152#issuecomment-787208614
+#if wxCHECK_VERSION(3, 1, 1)
+    if (sel_printers != sel_printers_prev) {
+#else
+    auto are_equal = [](const wxArrayInt& arr_first, const wxArrayInt& arr_second) {
+        if (arr_first.GetCount() != arr_second.GetCount())
+            return false;
+        for (size_t i = 0; i < arr_first.GetCount(); i++)
+            if (arr_first[i] != arr_second[i])
+                return false;
+        return true;
+    };
+    if (!are_equal(sel_printers, sel_printers_prev)) {
+#endif
+
         // Refresh type list
 		list_type->Clear();
 		list_type->append(_L("(All)"), &EMPTY);