maint: update to latest gnulib

Upstream gnulib recently patched a bug in bootstrap, for projects
that use a different name than build-aux for a subdirectory.  We
don't, but it doesn't hurt to update.

* .gnulib: Update, for bootstrap fix.
* bootstrap: Sync to upstream.
* bootstrap.conf: Match upstream bug fix.
Signed-off-by: NEric Blake <eblake@redhat.com>
(cherry picked from commit ac0852c7)

.gnulib @ 644c4049

-Subproject commit da8d59ee79138b85daee1ad5b22ea12e4fb6ce47
+Subproject commit 644c40496cf7d5a705a73c9dd32b035fcecc2ab1

bootstrap

@@ -256,12 +256,12 @@ esac
 # Extra files from gnulib, which override files from other sources.
 test -z "${gnulib_extra_files}" && \
   gnulib_extra_files="
-        $build_aux/install-sh
-        $build_aux/mdate-sh
-        $build_aux/texinfo.tex
-        $build_aux/depcomp
-        $build_aux/config.guess
-        $build_aux/config.sub
+        build-aux/install-sh
+        build-aux/mdate-sh
+        build-aux/texinfo.tex
+        build-aux/depcomp
+        build-aux/config.guess
+        build-aux/config.sub
         doc/INSTALL
 "
 

bootstrap.conf

@@ -232,10 +232,10 @@ touch AUTHORS ChangeLog || exit 1
 
 # Override bootstrap's list - we don't use mdate-sh or texinfo.tex.
 gnulib_extra_files="
-        $build_aux/install-sh
-        $build_aux/depcomp
-        $build_aux/config.guess
-        $build_aux/config.sub
+        build-aux/install-sh
+        build-aux/depcomp
+        build-aux/config.guess
+        build-aux/config.sub
         doc/INSTALL
 "