Revert "Drop dbus activation stub service"

This reverts commit 07125d24ee.

In contrast to what is claimed in #13396 dbus-broker apparently does
care for the service file to be around, and otherwise will claim
"Service Not Activatable" in the time between systemd starting up the
broker and connecting to it, which the stub service file is supposed to
make go away.

Reverting this makes the integration test suite pass again on host with
dbus-broker (i.e. current Fedora desktop).

Tested with dbus-broker-21-6.fc31.x86_64.

README

@@ -174,7 +174,9 @@ REQUIREMENTS:
         dependencies:
 
         util-linux >= v2.27.1 required
-        dbus >= 1.11.0 (strictly speaking optional, but recommended)
+        dbus >= 1.4.0 (strictly speaking optional, but recommended)
+                NOTE: If using dbus < 1.9.18, you should override the default
+                policy directory (--with-dbuspolicydir=/etc/dbus-1/system.d).
         dracut (optional)
         polkit (optional)
 

src/core/meson.build

@@ -195,6 +195,8 @@ endforeach
 
 install_data('org.freedesktop.systemd1.conf',
              install_dir : dbuspolicydir)
+install_data('org.freedesktop.systemd1.service',
+             install_dir : dbussystemservicedir)
 
 policy = configure_file(
         input : 'org.freedesktop.systemd1.policy.in',

src/core/org.freedesktop.systemd1.service

@@ -0,0 +1,13 @@
+#  SPDX-License-Identifier: LGPL-2.1+
+#
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[D-BUS Service]
+Name=org.freedesktop.systemd1
+Exec=/bin/false
+User=root

units/meson.build

@@ -310,6 +310,9 @@ install_data('user-.slice.d/10-defaults.conf',
 meson.add_install_script(meson_make_symlink,
                          join_paths(pkgsysconfdir, 'user'),
                          join_paths(sysconfdir, 'xdg/systemd/user'))
+meson.add_install_script(meson_make_symlink,
+                         join_paths(dbussystemservicedir, 'org.freedesktop.systemd1.service'),
+                         join_paths(dbussessionservicedir, 'org.freedesktop.systemd1.service'))
 if conf.get('HAVE_SYSV_COMPAT') == 1
         foreach i : [1, 2, 3, 4, 5]
                 meson.add_install_script(