build: avoid test warnings on mingw

* .gnulib: Update to latest, for getaddrinfo fixes.
Reported by Matthias Bolte.

diff --git a/.gnulib b/.gnulib
index 7d06b32684363a39fae65c616b84bc7589768106..3864a29763baff1d01895a57f73729fd53cc5fbf 160000 (submodule)
--- a/.gnulib
+++ b/.gnulib
@@ -1 +1 @@
-Subproject commit 7d06b32684363a39fae65c616b84bc7589768106
+Subproject commit 3864a29763baff1d01895a57f73729fd53cc5fbf