RcppParallel provides parallel programming primitives used by the Stan
ecosystem (StanHeaders, rstan) and other packages for Bayesian statistical
modeling.
The upstream package bundles Intel TBB, which does not support FreeBSD as a
build target. This port links against the system onetbb (devel/onetbb) instead.
Signed-off-by: Christos Longros <chris.longros@gmail.com>