abc9_ops: optimise to not derive unless attribute exists
abc9_ops: optimise to not derive unless attribute exists

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