build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 26c0590f06332c3a2f3e7e12a96f19a58f723fe2..f782c0f66728e636e98214c33e55de063f00f113 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 26c0590f06332c3a2f3e7e12a96f19a58f723fe2
+Subproject commit f782c0f66728e636e98214c33e55de063f00f113