Allow conda-build to remove the work directory.
Allow conda-build to remove the work directory.

As there is now nothing else we require from the work directory
(particularly the tests), allow conda-build to remove it when the build
completes.

DudLab/rank_filter,nanshe-org/rank_filter,jakirkham/rank_filter,nanshe-org/rank_filter,nanshe-org/rank_filter,DudLab/rank_filter,jakirkham/rank_filter,jakirkham/rank_filter,DudLab/rank_filter