Get wayland-session wrapper from environment.

diff --git a/daemon/gdm-session.c b/daemon/gdm-session.c
index 3b83fcd3..e60e6a57 100644
--- a/daemon/gdm-session.c
+++ b/daemon/gdm-session.c
@@ -2933,8 +2933,9 @@ gdm_session_start_session (GdmSession *self,
                                                            allow_remote_connections? "--allow-remote-connections " : "",
                                                            command);
                         } else {
-                                program = g_strdup_printf (LIBEXECDIR "/gdm-wayland-session %s\"%s\"",
+                                program = g_strdup_printf (LIBEXECDIR "/gdm-wayland-session %s\"%s %s\"",
                                                            register_session ? "--register-session " : "",
+                                                           g_getenv ("GDM_WAYLAND_SESSION"),
                                                            command);
                         }
                 } else if (run_xsession_script) {
@@ -2965,8 +2966,9 @@ gdm_session_start_session (GdmSession *self,
                                                            register_session ? "--register-session " : "",
                                                            self->selected_program);
                         } else {
-                                program = g_strdup_printf (LIBEXECDIR "/gdm-wayland-session %s\"dbus-run-session -- %s\"",
+                                program = g_strdup_printf (LIBEXECDIR "/gdm-wayland-session %s\"dbus-run-session -- %s %s\"",
                                                            register_session ? "--register-session " : "",
+                                                           g_getenv ("GDM_WAYLAND_SESSION"),
                                                            self->selected_program);
                         }
                 } else {
guix/log/?id=211ea54122f3f72220dbe39dfbb86e506be925b9'>root</a>/<a href='/guix/log/bootstrap?id=211ea54122f3f72220dbe39dfbb86e506be925b9'>bootstrap</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/bootstrap?id=211ea54122f3f72220dbe39dfbb86e506be925b9&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-06-13 20:46:01 +0200'>2021-06-13</span></td><td><a href='/guix/commit/bootstrap?id=bd02e50a02ceed914135dba1e69e4457e489cf86'>bootstrap: Simplify search for translation languages.</a><span class='msg-avail'>...<span class='msg-tooltip'>Extend the sed script to also behave like "basename",
saving the addtional call of "xargs basename".

* bootstrap (langs): Extend sed scripts, remove running xargs.
</span></span></td><td>Hartmut Goebel</td></tr>
<tr><td><span title='2020-02-17 11:49:08 +0100'>2020-02-17</span></td><td><a href='/guix/commit/bootstrap?id=3dd311e3a059131ef245417106d4fb659222ef3c'>bootstrap: Fix typo.</a><span class='msg-avail'>...<span class='msg-tooltip'>* bootstrap: Substitute ‘guix-cookbook’ for copy/pasted ‘guix-manual’.

Reported-by: jetomit on #guix
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-09-18 11:38:14 +0200'>2019-09-18</span></td><td><a href='/guix/commit/bootstrap?id=7bc46ecc34ceb042ff890e5d306d0a2a736e891d'>doc: Add Guix Cookbook.</a><span class='msg-avail'>...<span class='msg-tooltip'>* .gitignore: Update ignore list.
* Makefile.am (assert-no-store-file-names): Exclude the cookbook.
* bootstrap: Generate po files for cookbook translations.
* doc/guix-cookbook.texi: New file.
* doc/local.mk (info_TEXINFOS): Add it; add a rule to build cookbook
translations.
* po/doc/local.mk (DOC_COOKBOOK_PO_FILES): New variable.
(EXTRA_DIST): Add cookbook pot file and po files.
(doc-po-update-cookbook-%): New target.
(doc-pot-update): Also update cookbook pot file.
(doc-po-update): Also update cookbook po files.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2019-04-26 11:21:32 +0200'>2019-04-26</span></td><td><a href='/guix/commit/bootstrap?id=9ca5ff882e2ac4eaab02eb0fde545bd784af478b'>bootstrap: Break automake dependency on generated files.</a><span class='msg-avail'>...<span class='msg-tooltip'>* bootstrap: Generate stub files for the manual translations whose
generated files are not included in the VCS.
* doc/contributing.de.texi: Remove file.
* doc/contributing.es.texi: Remove file.
* doc/contributing.fr.texi: Remove file.
* doc/contributing.zh_CN.texi: Remove file.
* doc/guix.de.texi: Remove file.
* doc/guix.es.texi: Remove file.
* doc/guix.fr.texi: Remove file.
* doc/guix.zh_CN.texi: Remove file.
* .gitignore: Add them.

Signed-off-by: Julien Lepiller &lt;julien@lepiller.eu&gt;
</span></span></td><td>Miguel Ángel Arruga Vivas</td></tr>