build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 5528e726e9cc1ff9a2c7a71100450c52b65e9e7f..b2555cf7d1275c29d6190355143e6f92dbf77432 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 5528e726e9cc1ff9a2c7a71100450c52b65e9e7f
+Subproject commit b2555cf7d1275c29d6190355143e6f92dbf77432