build: update gnulib submodule to latest

eggert · eggert · commit 86ece0ee2169 · 2019-01-06T17:23:17.000-08:00
diff --git a/gnulib b/gnulib
@@ -1 +1 @@
-Subproject commit 10652b56fe5b76370187a06296168cff9cffb730
+Subproject commit 8089c00979a5b089cff592c6b91420e595657167
