scripts/functions: if no upstream URL is given, silently ignore that

When retrieving tarballs from upstream, if no URL was given, do not
fail; simmply ignore that fact.

This will be used later when the SVN helper will call the standard
helper to try the LAN mirror before trying svn.

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

# Compute Blackfin-specific values

CT_DoArchTupleValues() {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="bfin"

    # gcc ./configure flags

    CT_ARCH_WITH_ARCH=

    CT_ARCH_WITH_ABI=

    CT_ARCH_WITH_CPU=

    CT_ARCH_WITH_TUNE=

    CT_ARCH_WITH_FPU=

    CT_ARCH_WITH_FLOAT=

}