build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 20074698382b7e4f049f52bbdeaf6a39508a8601..814a1087ca7b8269949802faf73cc41daed34248 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 20074698382b7e4f049f52bbdeaf6a39508a8601
+Subproject commit 814a1087ca7b8269949802faf73cc41daed34248