Merge branch 'focal-buildd-fix-dns' of lp:~davidkrauser/livecd-rootfs/+git/livecd-rootfs into ubuntu/master

Safely set /etc/resolv.conf to an empty file in buildd images

MP: https://code.launchpad.net/~davidkrauser/livecd-rootfs/+git/livecd-rootfs/+merge/381316

live-build/buildd/hooks/49-empty-resolv-conf.binary

@@ -1,4 +1,3 @@
-#!/bin/sh
-set -e
-
-chroot chroot truncate -s 0 /etc/resolv.conf
+#!/bin/sh -e
+chroot chroot rm /etc/resolv.conf
+chroot chroot touch /etc/resolv.conf