Set LC_NUMERIC=C when --robot is used.

It is to ensure that floating point numbers
will always have a dot as the decimal separator.

src/xz/args.c

@@ -222,6 +222,10 @@ parse_real(args_info *args, int argc, char **argv)
 		// --robot
 		case OPT_ROBOT:
 			opt_robot = true;
+
+			// This is to make sure that floating point numbers
+			// always have a dot as decimal separator.
+			setlocale(LC_NUMERIC, "C");
 			break;
 
 		case 'z':