Nobody… Arch Linux has the latest glibc release (2.20) so is not affected by the GHOST bug, which was fixed upstream in glibc-2.18 (without realising the security implications).
For those that want to know more about security issues and updates in Arch Linux, check out the arch-security mailing list.
Wait, there is security bug in glibc? and Arch system is not affected because of rolling release … nothing news.
I will call Pacman, to eat Ghost/Phantoms!
Pun intended.