build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 667561d720dd1e22b51fe5d308a8f94d49d46b85..908690cb743e69c73b42ae310807b29800c8764b 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 667561d720dd1e22b51fe5d308a8f94d49d46b85
+Subproject commit 908690cb743e69c73b42ae310807b29800c8764b