comp-libs/cloog: new versions have the version number in the dir name

For CLooG/PPL 0.15.3, the directory name was simply cloog-ppl.
For any later versions, the driectory name does have the version, such as
cloog-ppl-0.15.4.

# Compute Alpha-specific values

CT_DoArchTupleValues () {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="${CT_ARCH}${CT_ARCH_ALPHA_VARIANT}"

    # The kernel ARCH:

    CT_KERNEL_ARCH=${CT_ARCH}

}