Fix creating the .../lib/ directory structure in the non-sysroot case

The symbol link that is created in the sysroot directory only needs
to be made when the cross compiler is build with the sysroot option

Signed-off-by: Bart van der Meulen <bartvdrmeulen@gmail.com>
(transplanted from 0e49e6eddac4f5bbde6394eb3e6e36be75fc550c)

# Compute x86_64-specific values

CT_DoArchTupleValues() {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="${CT_ARCH}"

}