Use newly-renamed -push-copy option.

passes/sat/qbfsat.cc

@@ -483,7 +483,7 @@ struct QbfSatPass : public Pass {
 		if (!opt.specialize_from_file) {
 			//Save the design to restore after modiyfing the current module.
 			std::string module_name = module->name.str();
-			Pass::call(design, "design -duplicate");
+			Pass::call(design, "design -push-copy");
 
 			//Replace input wires with wires assigned $allconst cells.
 			std::set<std::string> input_wires = validate_design_and_get_inputs(module, opt);