Compilation of the share library .so ?

[paugier]

For fluidfft, we need the shared library of p3dfft. On the clusters, the modules created from p3dfft master do not contained the shared library.

We need to compile this fork https://github.com/CyrilleBonamy/p3dfft to produce the share library. It would be much nicer if it could be possible to produce the shared library with the main repository of p3dfft.