There is none. If a block is not used, it might get optimized away.
If you want to do this, the easiest way to do it would be to add virtual pin assignments in the Assignment Editor on the outputs of the block.
you can set it as a design partition, once it is set. Usually, it wouldn't simply optimized away the output of your block ram. But you had to make sure that your output of the ram is in the boundary of the design partition.