build: update gnulib to fix a tests build failure

* gnulib: Update to incorporate a fix for building tests
with -Werror=old-style-declaration

diff --git a/gnulib b/gnulib
index 8b5510050ddbf5bdee4a7cb89f8ee32e08aecd94..0658e5039f75053480a7599edca236fecffe100d 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit 8b5510050ddbf5bdee4a7cb89f8ee32e08aecd94
+Subproject commit 0658e5039f75053480a7599edca236fecffe100d