Simplify JH build options.
Simplify JH build options.

- Remove old arguments pertaining to building dependencies from source.
- Use DELIGHT and ARNOLD_ROOT to find renderers in platform independent way.
- Remove unused getOption() function.

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