Actually cardio has the effect of helping the body to partition nutrients more efficiently, by increasing blood flow the muscles and altering metabolic processes. Also research has shown that most people end up eating more calories than they burn from the cardio due to a vastly increased appetite. This will only help one to build more LBM in the long run. If you want to maximize total weight gain then sure don't do cardio. But you will gain a lot of fat and water in addition to LBM.