build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 53701517c6517e5161e4533e44c33b5e4db17314..4ea0e64a8db7064427f6aa5624a4efd4b41db132 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 53701517c6517e5161e4533e44c33b5e4db17314
+Subproject commit 4ea0e64a8db7064427f6aa5624a4efd4b41db132