Enable systemd as part of image creation

Microsoft offically support systemd now and our Pro service relies on
it. This option is enabled by default via our launcher (Windows-side) on
first run for quite a while.
Remve this file creation from it, don’t ship it in a package as the
file may be altered by the user to add additional options and ship it as
part of the rootfs.

Co-authored-by: Jean-Baptiste Lallement <jean-baptiste@ubuntu.com>

live-build/ubuntu-wsl/hooks/00-enable-systemd.chroot

@@ -0,0 +1,10 @@
+#!/bin/bash -eu
+# vi: ts=4 expandtab
+#
+#	Enable systemd by default on our WSL image
+#
+
+cat <<EOF >/etc/wsl.conf
+[boot]
+systemd=true
+EOF