build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 8a0efd04dc9583c96b4a0d3c311ff216e07dcdcd..c46ae39631773a7fdae7d171cc4ef0bf2123efff 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 8a0efd04dc9583c96b4a0d3c311ff216e07dcdcd
+Subproject commit c46ae39631773a7fdae7d171cc4ef0bf2123efff