synth_intel: Warn about untested Quartus backend
synth_intel: Warn about untested Quartus backend

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