build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index db37bb3e918ce69fd0bf5e45752edd07f49ae07d..add53559b5d05734b3b6b5ad5ec8333019e74703 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit db37bb3e918ce69fd0bf5e45752edd07f49ae07d
+Subproject commit add53559b5d05734b3b6b5ad5ec8333019e74703