build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 09ba76e4c6a04d7b19bfe08cef12c29ddd21734c..77a06aac2187e2ea13e5b7aa8e30d46a81ca45f8 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 09ba76e4c6a04d7b19bfe08cef12c29ddd21734c
+Subproject commit 77a06aac2187e2ea13e5b7aa8e30d46a81ca45f8