Don't install systemd units unless using libsystemd session tracking.

Submitted upstream:

  https://gitlab.freedesktop.org/polkit/polkit/-/merge_requests/134

diff --git a/data/meson.build b/data/meson.build
--- a/data/meson.build
+++ b/data/meson.build
@@ -26,7 +26,7 @@ if enable_pam
   )
 endif
 
-if enable_logind
+if session_tracking == 'libsystemd-login'
   configure_file(
     input: 'polkit.service.in',
     output: '@BASENAME@',
diff --git a/meson.build b/meson.build
--- a/meson.build
+++ b/meson.build
@@ -199,7 +199,7 @@ if enable_logind
 
   # systemd unit / service files
   systemd_systemdsystemunitdir = get_option('systemdsystemunitdir')
-  if systemd_systemdsystemunitdir == ''
+  if systemd_systemdsystemunitdir == '' and session_tracking == 'libsystemd-login'
     systemd_dep = dependency('systemd', not_found_message: 'systemd required but not found, please provide a valid systemd user unit dir or disable it')
     # FIXME: systemd.pc file does not use variables with relative paths, so `define_variable` cannot be used
     systemd_systemdsystemunitdir = systemd_dep.get_pkgconfig_variable('systemdsystemunitdir')
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<div class='path'>path: <a href='/guix/log/?id=b73b056abbed1b031360b8cbb1a8e23aa07bca60'>root</a>/<a href='/guix/log/etc?id=b73b056abbed1b031360b8cbb1a8e23aa07bca60'>etc</a>/<a href='/guix/log/etc/git?id=b73b056abbed1b031360b8cbb1a8e23aa07bca60'>git</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/git?id=b73b056abbed1b031360b8cbb1a8e23aa07bca60&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-11-07 12:33:25 -0500'>2023-11-07</span></td><td><a href='/guix/commit/etc/git?id=889a6204f871fa47ba1ce12bf4a5e9600576f86a'>doc: Add some guidelines for reviewing.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/contributing.texi (Contributing) [Reviewing the Work of Others]: New
section.
(Debbugs Usertags): Expound with Emacs Debbugs information and document the
'reviewed-looks-good' usertag.
* etc/git/gitconfig [b4]: New section.

Change-Id: I56630b15ec4fbc5c67e5420dbf2838556a005d6b
Reviewed-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-10-22 16:09:04 -0400'>2023-10-22</span></td><td><a href='/guix/commit/etc/git?id=8005e09b261d65bf0f7469cd8e89423c1c1db820'>build: Add a commit-msg hook that embeds Change-Id in commit messages.</a><span class='msg-avail'>...<span class='msg-tooltip'>Partially implements &lt;https://issues.guix.gnu.org/66027&gt;.

This will make it possible to track a merged commit back to its original
posting on the mailing list, and open the door to new opportunities such as
closing fully merged series automatically.

* Makefile.am (COMMIT_MSG_MAGIC): New variable.
(.git/hooks/commit-msg): New target.
* etc/git/commit-msg: New file.
* doc/contributing.texi (Configuring Git): Document Change-Id.

Series-changes: 3
 - Clarify documentation text, as suggested by Simon
Change-Id: Ia92fa958eae600fdd4e180bad494c85db8bb4dd6
Reviewed-by: Simon Tournier &lt;zimon.toutoune@gmail.com&gt;
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-05-18 23:17:31 -0400'>2023-05-18</span></td><td><a href='/guix/commit/etc/git?id=03b453cfe54756bcec6b7c7dfaf71566d84c7a75'>etc: gitconfig: Do not enforced signed commits.</a><span class='msg-avail'>...<span class='msg-tooltip'>This change was more invasive than initially thought, and cannot be disabled
easily, as raised by a few people.  Let's revert it for now.  At least the
pre-push hook should be deployed automatically and catch any unsigned commits
attempted to be pushed to Savannah.

* etc/git/gitconfig [commit]: Remove section.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2023-05-01 12:39:11 -0400'>2023-05-01</span></td><td><a href='/guix/commit/etc/git?id=8b972da068708a8b17f3ab153ea940690ca49ca9'>Makefile.am: Auto-configure Git on 'make'.</a><span class='msg-avail'>...<span class='msg-tooltip'>This means we do not need to worry anymore about manually syncing the pre-push
git hook or the Guix-provided git configuration.

* etc/git/gitconfig: Augment configuration template with useful options to
allow for auto-configuration.
* Makefile.am (.git/hooks/pre-push, .git/config): New targets.
(nodist_noinst_DATA): New primary variable holding the above targets.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-10-14 00:24:34 +0200'>2021-10-14</span></td><td><a href='/guix/commit/etc/git?id=f8b10932c86cf4c1657a67e8c484d76f757b64bd'>Add git configuration templates to improve diff hunk header detection.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a follow-up to commit 9fc8ae4171e5da4939a64fc6d684c8b9d85bbe84, which
missed two hunks from &lt;https://issues.guix.gnu.org/50363&gt;.

Reported by hackeryarn on #guix.

* .gitattributes, etc/git/gitconfig: New files.

Signed-off-by: Marius Bakke &lt;marius@gnu.org&gt;
</span></span></td><td>Sarah Morgensen</td></tr>
<tr><td><span title='2020-12-14 12:15:06 -0500'>2020-12-14</span></td><td><a href='/guix/commit/etc/git?id=80ebcdd100a82fdc582e62f35042c74ce38ea753'>maint: Only run `make authenticate` when pushing commits.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/git/pre-push: Exit early when deleting a branch.
</span></span></td><td>Leo Famulari</td></tr>
<tr><td><span title='2020-06-01 00:51:38 +0200'>2020-06-01</span></td><td><a href='/guix/commit/etc/git?id=6f6758c45d3913dbf98bb8e50f21f7bfb25b40ea'>maint: Adjust comment in 'pre-push' hook.</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/git/pre-push: Adjust comment.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-29 18:31:38 +0200'>2020-05-29</span></td><td><a href='/guix/commit/etc/git?id=e65a44649e8d7698c4a888f1de625a67052520e9'>maint: Git pre-push hook runs "make authenticate check-channel-news".</a><span class='msg-avail'>...<span class='msg-tooltip'>* etc/git/pre-push: Change to run "make authenticate check-channel-news".
</span></span></td><td>Ludovic Courtès</td></tr>