build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 481f709ceba803288289da8e11a52d309d0fc9a1..cf8ddf08dec79be620c011ce204cbdb6bff35c50 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 481f709ceba803288289da8e11a52d309d0fc9a1
+Subproject commit cf8ddf08dec79be620c011ce204cbdb6bff35c50