build: update from gnulib

* gnulib: Update submodule to latest.

diff --git a/gnulib b/gnulib
index 077d9afeabe70728bec79f7ea9eff0264a7fccdc..3ef64012bf653379fda629f5a6b619be4c1f2e69 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 077d9afeabe70728bec79f7ea9eff0264a7fccdc
+Subproject commit 3ef64012bf653379fda629f5a6b619be4c1f2e69