Revert "Create /etc/resolv.conf as a relative symlink"

Something about the relative symlink makes arch-chroot go haywire
when invoked by `build.sh` and create crazy bind mounts like
/tmp/boxes-tmp/tmp.cwtHQPvydE/mount/tmp/boxes-tmp/tmp.cwtHQPvydE/mount/run/systemd/resolve/stub-resolv.conf

Revert to an absolute symlink until the issue is fixed.
See https://github.com/archlinux/arch-install-scripts/issues/55

This reverts commit ff22bfc4.

images/base.sh

@@ -18,7 +18,7 @@ function pre() {
   echo -e "/swap/swapfile none swap defaults 0 0" >>"${MOUNT}/etc/fstab"
 
   arch-chroot "${MOUNT}" /usr/bin/systemd-firstboot --locale=C.UTF-8 --timezone=UTC --hostname=archlinux --keymap=us
-  ln -sf ../run/systemd/resolve/stub-resolv.conf "${MOUNT}/etc/resolv.conf"
+  ln -sf /run/systemd/resolve/stub-resolv.conf "${MOUNT}/etc/resolv.conf"
 
   # Setup pacman-init.service for clean pacman keyring initialization
   cat <<EOF >"${MOUNT}/etc/systemd/system/pacman-init.service"