Please add "compliance" target to riviera.mk

Hi @dawidzim . As of #406 the compliance regression has the ability to dump compliance test signatures and compare them to the reference signatures provided in compliance test-suite. More information is available in the UVM README.

This update requires a simulator-specific compliance target to be added to each <sim>.mk Can you add this for riviera.mk? Check out xrun, dsim or vsim for a working example.

Thanks!