libxl: add explicit linkage to xenstore library

Since

  commit eee7bd4e
  Author: Joao Martins <joao.m.martins@oracle.com>
  Date:   Tue Jul 26 00:45:14 2016 +0100

    libxl: implement virDomainBlockStats

    Introduce initial support for domainBlockStats API

the libxl driver calls a couple of xenstore APIs, so it must explicitly
link to this library rather than rely on indirect linkage via libxl or
other xen libraries.
Reviewed-by: NJim Fehlig <jfehlig@suse.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

m4/virt-driver-libxl.m4

@@ -75,9 +75,9 @@ AC_DEFUN([LIBVIRT_DRIVER_CHECK_LIBXL], [
     dnl (since Xen 4.7) if not then assume it is in libxenctrl
     dnl (as it was for 4.6 and earler)
     AC_CHECK_LIB([xentoollog], [xtl_createlogger_stdiostream], [
-      LIBXL_LIBS="$LIBXL_LIBS -lxentoollog"
+      LIBXL_LIBS="$LIBXL_LIBS -lxenstore -lxentoollog"
     ],[
-      LIBXL_LIBS="$LIBXL_LIBS -lxenctrl"
+      LIBXL_LIBS="$LIBXL_LIBS -lxenstore -lxenctrl"
     ])
 
     dnl Check if libxl_domain_config_from_json is available for domXML to