build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 6eedb6a104486c2df4384195e5dfc487d97c5beb..bd399f07ee4f383fad038efad25a659fcdc0bbb0 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 6eedb6a104486c2df4384195e5dfc487d97c5beb
+Subproject commit bd399f07ee4f383fad038efad25a659fcdc0bbb0