Starting from GLib 2.49, the gdbus-codegen tool automatically generates
the auto cleanup symbols for the GDBus proxy and skeleton interfaces.
Since we don't depend on a specific version of GLib we need to
conditionally generate the auto cleanup symbols in case an older version
of gdbus-codegen is used when building Mutter.
This commit unbreaks the build under GNOME Continuous, which has been
failing with:
usr/include/glib-2.0/glib/gmacros.h:415:43: error: redefinition of 'glib_autoptr_cleanup_Login1Session'
#define _GLIB_AUTOPTR_FUNC_NAME(TypeName) glib_autoptr_cleanup_##TypeName
^
[...]
/usr/include/glib-2.0/glib/gmacros.h:415:43: note: previous definition of 'glib_autoptr_cleanup_Login1Session' was here
./meta-dbus-login1.h:82:1: note: in expansion of macro 'G_DEFINE_AUTOPTR_CLEANUP_FUNC'
G_DEFINE_AUTOPTR_CLEANUP_FUNC (Login1Session, g_object_unref)
^
aeda556af1