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 x86_64-specific values

 CT_DoArchTupleValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}"

 }