This fixes the obsolescence warning for AC_TRY_RUN with autoconf 2.70+:

  $ ./boot.sh
  configure.ac:141: warning: The macro `AC_TRY_RUN' is obsolete.
  configure.ac:141: You should run autoupdate.
  ./lib/autoconf/general.m4:2997: AC_TRY_RUN is expanded from...
  lib/m4sugar/m4sh.m4:692: _AS_IF_ELSE is expanded from...
  lib/m4sugar/m4sh.m4:699: AS_IF is expanded from...
  ./lib/autoconf/general.m4:2249: AC_CACHE_VAL is expanded from...
  ./lib/autoconf/general.m4:2270: AC_CACHE_CHECK is expanded from...
  m4/ax_func_posix_memalign.m4:27: AX_FUNC_POSIX_MEMALIGN is expanded from...
  configure.ac:141: the top level

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>