Build gcc 4.1.0 so i can target both x86 and AMD64

[Richard Homolka]

Hello, i just built gcc 4.1.0 from sources.  I'd like to be able to target 
both 32 bit and 64 bit apps.  I try to add the -m64 flag to a compile though 
and i get:
hello.c:1: sorry, unimplemented: 64-bit mode not compiled in

what did i do wrong in the build?  i didn't see anything about targetting 
multiple configs.
My configure command is:
../gcc-4.*/configure \
        --prefix=/tp/tools/gcc/4.1.0 \
        --enable-shared \
        --enable-threads \
        --enable-tls \
        --with-arch=pentium3 \
        --with-tune=pentium4 \
        --enable-__cxa_atexit \
        --enable-languages=c,c++,fortran \
        --disable-nls \
        --with-gmp=$GMPDIR \
        --with-mpfr=$MPFRDIR

any tips? thank you