fix libxl build failure

Fix libxl build issue caused by 21966, which adds the hidden attribute,
but didn't update the tools/libxl/xenguest.c.

Signed-off-by: Jiang, Yunhong <yunhong.jiang@intel.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
committer: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

tools/libxl/xenguest.c

@@ -20,6 +20,7 @@
 #include <string.h>
 
 #include "libxl.h"
+#include "libxl_internal.h"
 
 int hvm_build_set_params(xc_interface *handle, uint32_t domid,
                          libxl_domain_build_info *info,