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/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)