build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 64042bb91aea5f854ca8a8938e2b3f7d1935e4f1..955360a66c99bdd9ac3688519a8b521b06958fd3 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 64042bb91aea5f854ca8a8938e2b3f7d1935e4f1
+Subproject commit 955360a66c99bdd9ac3688519a8b521b06958fd3