lib and lib64 on x86_64 arch, how to change?

[Leonid Petrov <user3@xxxxxxxxxxx>]

Hello,

  I compile gcc-4.3.2 on x86_64 processor, 64-bit Linux and 
configure gcc as ../configure --prefix=$G/opt --enable-shared \
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu \
--with-mpfr=$G/opt --with-gmp=$G/opt 
--enable-languages=c,c++,fortran,java,objc,obj-c++ 

  When I run make install, among others, two directories are created:
$G/opt/lib with legacy 32-bit libraries and $G/opt/lib64 
with 64-bit libraries. My question is how I can force 
the build process to put 64-bit libraries in $G/opt/lib and
legacy 32-bit libraries in $G/opt/lib32 ?

Leonid Petrov