IEEE Packing: fix test failure

tests/grib_packing_order.sh

@@ -82,6 +82,11 @@ if [ $HAVE_EXTRA_TESTS -eq 1 ]; then
 
     # No point comparing with grid_simple as grid_ieee will be closer to the actual values
     # and less lossy
+
+    # Test with environment variable
+    ECCODES_GRIB_IEEE_PACKING=32 \
+       $EXEC ${test_dir}/grib_packing_order grid_simple packing_type_before_values $temp_ieee1
+    grib_check_key_equals $temp_ieee1 packingType grid_ieee
 fi