[gnome-settings-daemon] Add an --enable-systemd option to configure

[Bastien Nocera <hadess src gnome org>]

commit 4f97b6430588a369a040b629b9c8429d89f1818e
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Dec 23 22:22:53 2011 -0500

    Add an --enable-systemd option to configure
    
    The SYSTEMD_CFLAGS and _LIBS will be used in the following
    commits.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=666787

 configure.ac |   23 +++++++++++++++++++++++
 1 files changed, 23 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index a07d422..5311034 100644
--- a/configure.ac
+++ b/configure.ac
@@ -290,6 +290,28 @@ dnl ==============================================
 PKG_CHECK_MODULES(UPOWER, upower-glib >= $UPOWER_REQUIRED_VERSION libcanberra-gtk3)
 
 # ---------------------------------------------------------------------------
+# systemd
+# ---------------------------------------------------------------------------
+
+AC_ARG_ENABLE([systemd],
+              AS_HELP_STRING([--enable-systemd], [Use systemd for session tracking]),
+              [with_systemd=$enableval],
+              [with_systemd=no])
+if test "$with_systemd" = "yes" ; then
+  PKG_CHECK_MODULES(SYSTEMD, [libsystemd-login])
+  AC_DEFINE(HAVE_SYSTEMD, 1, [Define if systemd is used for session tracking])
+  SESSION_TRACKING=systemd
+else
+  SESSION_TRACKING=ConsoleKit
+fi
+
+AC_SUBST(SYSTEMD_CFLAGS)
+AC_SUBST(SYSTEMD_LIBS)
+
+AM_CONDITIONAL(WITH_SYSTEMD, [test "$with_systemd" = "yes"], [Using systemd])
+
+
+# ---------------------------------------------------------------------------
 # CUPS
 # ---------------------------------------------------------------------------
 
@@ -478,6 +500,7 @@ echo "
         cflags:                   ${CFLAGS}
         Maintainer mode:          ${USE_MAINTAINER_MODE}
 
+        Session tracking:         ${SESSION_TRACKING}
         LCMS DICT support:        ${have_new_lcms}
 
         Libnotify support:        ${have_libnotify}