fop(1), hru(1), intcmp(1), mm(1), rpn(1), swab(1): fixes conditional compilation

src/hru.rs

@@ -86,7 +86,7 @@ fn main() -> ExitCode {
 		return ExitCode::from(EX_USAGE as u8);
 	}
 
-	if cfg!(target_os="openbsd") {
+	#[cfg(target_os="openbsd")] {
 		let promises = Promises::new("stdio");
 		if let Err(e) = pledge(Some(promises), None) {
 			eprintln!("{}: {}", argv[0], e.strerror());