libsForQt5.qca-qt5: mark as broken on darwin

pkgs/development/libraries/qca-qt5/default.nix

@@ -26,5 +26,8 @@ stdenv.mkDerivation rec {
     maintainers = with maintainers; [ ttuegel ];
     license = licenses.lgpl21Plus;
     platforms = with platforms; unix;
+    # until macOS SDK supports Qt 5.15, 2.3.2 is the highest version of qca-qt5
+    # that works on darwin
+    broken = stdenv.isDarwin;
   };
 }