MISC: good uid for /bin/su

So I don't know why but I tried to remaster the Archlinux install iso to get some custom stuff on it, and I couldn't use `su` while logged in as my user. An error about creating groups. It's just that I did not have the right uid set for this file, I corrected it by doing this:

chmod u+s /bin/su

And it's now fine.