build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index ec87cff2ac13f29f4aee88caa7e16e72cef3f490..53701517c6517e5161e4533e44c33b5e4db17314 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit ec87cff2ac13f29f4aee88caa7e16e72cef3f490
+Subproject commit 53701517c6517e5161e4533e44c33b5e4db17314