complibs/cloog: fix extraction

In the early days, cloog-ppl was bizarrely packaged: the first tarball
did not contain the version in the name of the extracted directory, so
we had to play tricks.

Nowadays, however, the first component of the path are stripped when
extracting a tarball, which means that the created directory will
always be properly named. So, our old tricks do no longer work, and
worse, they break the build.

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

 COPYING