complibs: fix using static companion libraries

When building a cross-compiler for a target which uses a file extension for
binaries the symbolic link to cc is not created correctly because the lookup
of the gcc binary is done in a incorrect path

Signed-off-by: Bart vdr. Meulen <bartvdrmeulen@gmail.com>

 # Compute s390-specific values

 CT_DoArchTupleValues() {

     # That's the only thing to override

     if [ "${CT_ARCH_64}" = "y" ]; then

         CT_TARGET_ARCH="s390x"

     fi

 }