First, you need to make sure you have a cross-compiler GCC and binutils (i.e. x86_64-w64-mingw32-[gcc,ld,dlltool,...]
) in PATH. Then, you can configure the mingw-w64-crt (do not use the toplevel configure itself) with:
/path/to/mingw-w64-crt/configure --host=x86_64-w64-mingw32 --enable-lib64 --disable-lib32
But the question is, why do you want to do this? There is a lot that can go wrong when building a toolchain, and there is a multitude of binaries available for virtually any platform.