Use libglnx

Starting down the path of not using libgsystem.  The main win here
will be code sharing between ostree/rpm-ostree as well as going down
the path of not using GFile * for local files.

src/libotutil/ot-variant-utils.c

@@ -133,7 +133,7 @@ ot_util_variant_map (GFile              *src,
                      GError            **error)
 {
   gboolean ret = FALSE;
-  gs_unref_variant GVariant *ret_variant = NULL;
+  g_autoptr(GVariant) ret_variant = NULL;
   GMappedFile *mfile = NULL;
 
   mfile = gs_file_map_noatime (src, NULL, error);

src/libotutil/otutil.h

@@ -26,6 +26,7 @@
 #include <libgsystem.h>
 #include <string.h> /* Yeah...let's just do that here. */
 #include <gsystem-local-alloc.h>
+#include <libglnx.h>
 
 #define ot_gobject_refz(o) (o ? g_object_ref (o) : o)