build: update gnulib submodule to latest

diff --git a/gnulib b/gnulib
index 100bccc49b23e2674a660653fa8036af3730f564..d984c0bca01a92fb06e2a0bca2042240953e7808 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 100bccc49b23e2674a660653fa8036af3730f564
+Subproject commit d984c0bca01a92fb06e2a0bca2042240953e7808