The `WITH_TBB` define needs to be set in order for code using the
various parallel threading helpers [1][2] to actually be multi-threaded.
The affected projects did not have `WITH_TBB` defined and were using the
single-thread variant of all affected APIs.
Additionally, in the case of `EnumerableThreadSpecific`, this results in
an ODR violation where there are 2 versions of the same class linked
into our final binary. One with TBB members and one without.
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[1] Namely code using the `BLI_task.hh`, `BLI_sort.hh`, and `BLI_enumerable_thread_specific.hh` headers
[2] `EnumerableThreadSpecific`, `parallel_for_each`, `parallel_reduce`, `parallel_invoke`, `isolate_task`, `parallel_sort`
Pull Request: https://projects.blender.org/blender/blender/pulls/124283
05241f47f5