This patch syncs a change to the top-level configury from gdb.  It
should not affect the gcc build at all.  Tested by rebuilding.

ChangeLog
2019-06-15  Tom Tromey  <tom@tromey.com>

	* configure.ac (host_libs): Add gnulib.
	* configure: Rebuild.
	* Makefile.def (host_modules, dependencies): Add gnulib.
	* Makefile.in: Rebuild.

From-SVN: r272332