archiso_pxe_common: remove resolv.conf before copy

Booting via PXE we want to keep our DNS configuration. So remove
/etc/resolv.conf in new root before copying the current file.

Without this systemd-resolved fallback nameservers are used and we see an
error message when the root ships a symbolic link to systemd-resolved's
stub-resolv.conf:

cp: not writing through dangling symlink '/new_root/etc/resolv.conf'

archiso/initcpio/hooks/archiso_pxe_common

@@ -73,6 +73,7 @@ run_latehook () {
                 ip link set "${netdev}" down
             done
         elif [ "${copy_resolvconf}" != "n" ] && [ -f /etc/resolv.conf ]; then
+            rm -f /new_root/etc/resolv.conf
             cp /etc/resolv.conf /new_root/etc/resolv.conf
         fi
     fi