This can't be built on powerpc because devel/tbb does not support 64-bits
atomics on ppc32 and forcing them does not help (as seen previously with
geo/osrm-backend). Spotted in the current macppc bulk.
OpenVDB is an Academy Award-winning open-source C++ library comprising a novel
hierarchical data structure and a suite of tools for the efficient storage and
manipulation of sparse volumetric data discretized on three-dimensional grids.
It was developed by DreamWorks Animation for use in volumetric applications
typically encountered in feature film production and is now maintained by the
Academy Software Foundation (ASWF).
