This is the solution proposed in the gentoo forums entry

limits.h (text/plain), 335 bytes, created by Robert Levin on 2005-04-13 05:08:29 UTC

/* Common header file autogenerated by create_ml_includes in multilib.eclass */

#ifndef __amd64__limits_h__
#define __amd64__limits_h__

#ifdef __i386__
#include "gentoo-multilib/x86/limits.h"
#endif /* __i386__ */

#ifdef __x86_64__
#include "gentoo-multilib/amd64/limits.h"
#endif /* __x86_64__ */

#endif /* __amd64__limits_h__ */