build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index ff4b084a68a7141d4e5842e4ba2b23050c896a27..814a1087ca7b8269949802faf73cc41daed34248 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit ff4b084a68a7141d4e5842e4ba2b23050c896a27
+Subproject commit 814a1087ca7b8269949802faf73cc41daed34248