live-installer: ensure sources.list is configured

By default, when you don't have any network or when you didn't enable
a network mirror, your sources.list is empty. We don't want this
so we hook into the finish-install step to make sure to set it up
if it's empty.

kali-config/common/includes.installer/usr/lib/finish-install.d/14fix-kali-sources-list

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+if grep -q '^deb ' /target/etc/apt/sources.list; then
+    echo "INFO: sources.list is configured, everything is fine"
+    exit 0
+fi
+
+echo "INFO: sources.list is empty, setting up a default one for Kali"
+
+cat >/target/etc/apt/sources.list <<END
+# See https://www.kali.org/docs/general-use/kali-linux-sources-list-repositories/
+deb http://http.kali.org/kali kali-rolling main contrib non-free
+
+# Additional line for source packages
+# deb-src http://http.kali.org/kali kali-rolling main contrib non-free
+END
+in-target apt-get update || true