Makefile, swab(1): fixes swab build

src/swab.rs

@@ -53,7 +53,7 @@ fn main() -> ExitCode {
 			Ok("f") => force = true,
 			Ok("w") => {
 				if let Some(arg) = opt.arg() {
-					match opt.arg().parse::<usize>() {
+					match arg.parse::<usize>() {
 						Ok(w) if w % 2 == 0 => { wordsize = w; () },
 						_ => { return usage(&argv[0]); },
 					}