You want: --target i386-redhat-linux
however, this will only work if you have the glibc.i686 and glibc-devel.i686 installed AND you have to have a multiarch compiler capable of emitting 32- and 64-bit code at the same time.
GCC as delivered by Red Hat has been purposely castrated not to be able to do this, even though GCC is perfectly capable of doing it, and does so without much fuss on real UNIX operating systems such as AIX, Solaris, IRIX or even PPC-based Red Hat systems.
So in order to be able to do this, and if (and only if!) you want to use GCC to be able to do this, you must build and package your own version of GCC and explicitly enable a multiarch build, which the GCC ./configure script will not do by default if (and only if!) it detects that GCC is being built on GNU/Linux.
Other alternative would be to install and use either Intel, PGI, or Sun Studio compilers for GNU/Linux, but those compilers are far more pedantic and standards-compliant and will not tolerate many GCC non-portable syntax constructs.