su(1): bad auth_approval(3) failure handling

[Piotr Durlej]

Hello,

auth_approval(3) doesn't always set errno(2) on failure:

--- usr.bin/su/su.c.orig        Sat Dec  7 20:23:21 2019
+++ usr.bin/su/su.c     Fri Oct 30 14:38:11 2020
@@ -358,7 +358,7 @@ main(int argc, char **argv)
                err(1, "pledge");
 
        if (pwd->pw_uid && auth_approval(as, lc, pwd->pw_name, "su") == 0)
-               auth_err(as, 1, "approval failure");
+               auth_errx(as, 1, "approval failure");
        auth_close(as);
 
        execv(shell, np);