build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 9b07115f4a344effef1dde8bd0e6e356d4b0e744..6fd6098f510255c0b9134088b1526a50fef90edd 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 9b07115f4a344effef1dde8bd0e6e356d4b0e744
+Subproject commit 6fd6098f510255c0b9134088b1526a50fef90edd