build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 451042cb76d3f78f070c27ce8af6b6d215354681..a5a25302cc8d20832f08c828f1d2de0961607e0f 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 451042cb76d3f78f070c27ce8af6b6d215354681
+Subproject commit a5a25302cc8d20832f08c828f1d2de0961607e0f