Fixed clang build.
Fixed clang build.

TBB doesn't actually define the task_scheduler_init::automatic symbol, and clang wants to reference it rather than evaluate the constant. I don't quite understant it fully, but there's some detail on a similar problem here :

http://stackoverflow.com/questions/5391973/undefined-reference-to-static-const-int

andrewkaufman/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,hradec/gaffer,boberfly/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,goddardl/gaffer,andrewkaufman/gaffer,chippey/gaffer,lucienfostier/gaffer,GafferHQ/gaffer,hradec/gaffer,ivanimanishi/gaffer,boberfly/gaffer,hradec/gaffer,lucienfostier/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,chippey/gaffer,andrewkaufman/gaffer,boberfly/gaffer,goddardl/gaffer,hradec/gaffer,goddardl/gaffer,ivanimanishi/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,chippey/gaffer,ivanimanishi/gaffer,hradec/gaffer,chippey/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,ivanimanishi/gaffer,goddardl/gaffer,boberfly/gaffer,johnhaddon/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,GafferHQ/gaffer