Change gdbserver to use existing gnulib and libiberty

Change gdbserver to use existing gnulib and libiberty

This changes gdbserver so that it no longer builds its own gnulib and
libiberty.  Instead, it now relies on the ones that were already built
at the top level.

gdbsupport is still built specially for gdbserver.  This is more
complicated and will be tackled in a subsequent patch.

ChangeLog
2020-02-14  Tom Tromey  <tom@tromey.com>

	* Makefile.in: Rebuild.
	* Makefile.def: Make gdbserver require gnulib and libiberty.

gdbserver/ChangeLog
2020-02-14  Tom Tromey  <tom@tromey.com>

	* acinclude.m4: Don't include acx_configure_dir.m4.
	* Makefile.in (LIBIBERTY_BUILDDIR, GNULIB_BUILDDIR): Update.
	(SUBDIRS, CLEANDIRS, REQUIRED_SUBDIRS): Remove.
	(all, install-only, uninstall, clean-info, clean)
	(maintainer-clean): Don't recurse.
	(subdir_do, all-lib): Remove.
	($(LIBGNU) $(LIBIBERTY) $(GNULIB_H)): Remove rule.
	(GNULIB_H): Remove.
	(generated_files): Update.
	($(GNULIB_BUILDDIR)/Makefile): Remove rule.
	* configure: Rebuild.
	* configure.ac: Don't configure gnulib or libiberty.
	(GNULIB): Update.

gdbsupport/ChangeLog
2020-02-14  Tom Tromey  <tom@tromey.com>

	* common-defs.h: Change path to gnulib/config.h.

Change-Id: I469cbbf5db2ab37109c058e9e3a1e4f4dabdfc98