[mutter/gnome-3-28] build: Don't fail immediately when logind is missing

[Jonas Ådahl <jadahl src gnome org>]

commit 43d6c0ea61f257f24a3fbd9abb22d3e0a4ef9994
Author: Florian Müllner <fmuellner gnome org>
Date:   Thu Apr 26 16:07:32 2018 +0200

    build: Don't fail immediately when logind is missing
    
    We require logind for the native backend, but the backend itself is
    optional. However since commit 06c357d78, we will always throw an
    error if neither logind nor elogind are available, even when the
    backend is disabled.
    
    As we still support "auto" - that is, whether the native backend is
    enabled depends on whether its dependencies are available - the
    easiest option is to make sure we always include either elogind or
    libsystemd in the dependency check rather than erring out explicitly
    if neither is found.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/96
    
    
    (cherry picked from commit 82564772dc27c9b86270e5a694b04945d3f5e3a1)

 configure.ac | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index d9735eced..c98f583f9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -270,13 +270,10 @@ fi
 
 PKG_CHECK_MODULES(SYSTEMD, [libsystemd], [have_systemd=yes], [have_systemd=no])
 
-if test x$have_systemd = xyes; then
+if test x$have_systemd = xyes -o -z "$logind_provider"; then
      logind_provider="libsystemd"
 fi
 
-AS_IF([test -z "$logind_provider"],
-  AC_MSG_ERROR([Could not find either systemd or elogind as logind provider])])
-
 MUTTER_NATIVE_BACKEND_MODULES="libdrm $logind_provider libinput >= 1.4 gudev-1.0 gbm >= 10.3"
 
 AC_ARG_ENABLE(native-backend,