SConstruct : Add GAFFERCORTEX build option
SConstruct : Add GAFFERCORTEX build option

This can be used to disable building of the GafferCortex module.

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