maint: Update to latest gnulib

This pulls in, among other new things, vc-list-files fix to make
syntax-check work with git worktrees.
Signed-off-by: NErik Skultety <eskultet@redhat.com>

.gnulib @ 8d116e3f

-Subproject commit ce4ee4cbb596a9d7de2786cf8c48cf62a4edede7
+Subproject commit 8d116e3f657cb120f79efbbb675fa3cc9d21f53e