Prune /*NOTREACHED*/

This includes a simplification of mkbusy and format correctness in zhack
and ztest

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Issue #12201

cmd/zpool/zpool_main.c

@@ -429,10 +429,9 @@ get_usage(zpool_help_t idx)
 	case HELP_WAIT:
 		return (gettext("\twait [-Hp] [-T d|u] [-t <activity>[,...]] "
 		    "<pool> [interval]\n"));
+	default:
+		__builtin_unreachable();
 	}
-
-	abort();
-	/* NOTREACHED */
 }
 
 static void