build: update to latest gnulib

358 changes; most probably have no impact on libvirt, but we
might as well stay current.

* .gnulib: Update to latest.

diff --git a/.gnulib b/.gnulib
index da1717b7f93b77469f980ea5e13178e4e9e7ae09..2394a603e7586e671226478e5b15d924c3841f42 160000 (submodule)
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit da1717b7f93b77469f980ea5e13178e4e9e7ae09
+Subproject commit 2394a603e7586e671226478e5b15d924c3841f42