makefile: add support for built-in ghdl-yosys-plugin
makefile: add support for built-in ghdl-yosys-plugin

Co-authored-by: Tristan Gingold <de0926f9585d8b406e19da6c0524d24b4cc32b11@free.fr>
Co-authored-by: whitequark <b4701ebf9366004900e8211cdb469ccf92f5074c@whitequark.org>

antmicro/yosys,antmicro/yosys,antmicro/yosys,cliffordwolf/yosys,cliffordwolf/yosys,antmicro/yosys,cliffordwolf/yosys,cliffordwolf/yosys,cliffordwolf/yosys,YosysHQ/yosys,antmicro/yosys,YosysHQ/yosys,cliffordwolf/yosys,antmicro/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,YosysHQ/yosys,antmicro/yosys,cliffordwolf/yosys,cliffordwolf/yosys,antmicro/yosys,cliffordwolf/yosys,YosysHQ/yosys