When building without TBB use native to the platform spin lock
implementation. For Windows it is an atomic-based busy-wait,
for Linux it is pthreads' spin lock.
For macOS it is a mutex lock. The reason behind this is to stop
using atomics library which has been declared deprecated in SDK
version 10.12. So this changes fixes a lot of noisy warnings on
the newer SDK.
Differential Revision: https://developer.blender.org/D8180
