build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index e9943f52df74d2659f18e06803591b2384dba171..4f6545e79c4a7cd7feb2c8f23f1d5167e7165907 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit e9943f52df74d2659f18e06803591b2384dba171
+Subproject commit 4f6545e79c4a7cd7feb2c8f23f1d5167e7165907