debug/strace: 4.6 requires xz

strace 4.6 is only available as an XZ-compressed tarball.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from d878322997095e513c6311ec3713b83ca91e5d8c)

# Compute s390-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

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

        CT_TARGET_ARCH="s390x"

    fi

}