build: update gnulib submodule to latest

Fixes a test-lock failure on MacOS

diff --git a/gnulib b/gnulib
index 0481ab52033694e1c137d4911f4d025a186d1a2a..d3181471f95c870e9485be947608be84f7fe5325 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 0481ab52033694e1c137d4911f4d025a186d1a2a
+Subproject commit d3181471f95c870e9485be947608be84f7fe5325