[gentoo-amd64] How to install multilib'ed version of any library (for real multilib for x86 and x86_64 for every libraries)?

[Cheng Renquan <crquan@gmail.com>]

Hello, gentoo amd64 developers,
  I found a big problem with gentoo amd64 recently:

I'm just switching from x86 to amd64 gentoo, several months ago, everything
goes well, but now I have a project that need to compile some 32bit binaries;
since my gcc and glibc both have multilib support, originally I don't think it's
a problem, just like this hellworld.c program:

$ gcc -o hello helloworld.c             # will generate a default
hello executable, 64bit;
$ gcc -m32 -o hello.x86 helloworld.c # specify to generate a 32bit executable

So when I want to compile a separate software source, I just setenv
CC="gcc -m32"
this seems reasonable, but finally it failed with an error,

http://pastebin.org/52915

Now I know it's because of this software need 32bit libbfd, while the
default 64bit
libbfd is provided by sys-devel/binutils, so I need a multilib'ed
binutils library,
but how do I install a 32bit of libbfd in gentoo way?

Furthermore, if compiling any other 32bit program on gentoo-amd64, it may need
other more 32bit of libraries,

Comparing other linux distros like fedora-x86_64 and debian-amd64, I knew there
is simple way to archive this goal, just install both binutils.x86_64
and binutils.i686
packages, but on gentoo-amd64, how can we do this in a similarly simple way?

How about add USE multilib support of every package that contains libraries?

I have asked this problem on #gentoo-amd64 channel, but seemed no people
there knew it, so please someone on the mailing list know how to resolve it?

Thanks very much,

-- 
Cheng Renquan (程任全), from Singapore