build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index f5d93312df380b06ef375629be4c301f85fd6d9a..862a81c0e15448adde6a6e7473ec47e3a4bd91a6 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit f5d93312df380b06ef375629be4c301f85fd6d9a
+Subproject commit 862a81c0e15448adde6a6e7473ec47e3a4bd91a6