build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 6032b8a7017a04d49f92931b9f11e9b7a57bb302..46f9c21a08245fe224fd975de8632b04a0256387 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 6032b8a7017a04d49f92931b9f11e9b7a57bb302
+Subproject commit 46f9c21a08245fe224fd975de8632b04a0256387