build: update from gnulib

* gnulib: Update submodule to latest.

diff --git a/gnulib b/gnulib
index 7d8f602d6f6c1ac2633c23140c93aaca098c6a2a..53181ad5a87facb5d424a04d039606a8694ce261 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 7d8f602d6f6c1ac2633c23140c93aaca098c6a2a
+Subproject commit 53181ad5a87facb5d424a04d039606a8694ce261