build: update gnulib to fix a build warning/error in a test program

diff --git a/gnulib b/gnulib
index bac964725a412c590498aba68f6b9a8e723ae474..d72683055ea46253d8eb8f89341eff5414ae6ca0 160000 (submodule)
--- a/gnulib
+++ b/gnulib
@@ -1 +1 @@
-Subproject commit bac964725a412c590498aba68f6b9a8e723ae474
+Subproject commit d72683055ea46253d8eb8f89341eff5414ae6ca0