iverilog -s testbench -o ecp5evndemo_tb.vvp ecp5evndemo_tb.v ecp5evndemo.v `yosys-config --datdir/ecp5/cells_sim.v`
/usr/local/share/yosys/ecp5/cells_sim.v:820: Include file cells_ff.vh not found
ecp5evndemo.v:81: error: Unknown module type: USRMCLK
2 error(s) during elaboration.
*** These modules were missing:
        USRMCLK referenced 1 times.
***
make: *** [Makefile:114: ecp5evndemo_tb.vvp] Error 2