build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 3dfe3ab6c1f07982d8649fbc21078ddd7f010547..7606f1f29c58281b19cde8e14a0fea2ff638d2a5 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 3dfe3ab6c1f07982d8649fbc21078ddd7f010547
+Subproject commit 7606f1f29c58281b19cde8e14a0fea2ff638d2a5