scripts: do not download in // by default

Parallel downloads can be a bit harsh on the servers,
and some will fail (eg. uclibc.org) in some cases.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# Compute IA-64-specific values

CT_DoArchTupleValues() {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="${CT_ARCH}"

}