build fix - do not build volume viewer on MIC
build fix - do not build volume viewer on MIC

MengjiaoH/ospray,Twinklebear/OSPRay,MengjiaoH/ospray,ospray/OSPRay,favreau/OSPRay,MengjiaoH/ospray,ospray/OSPRay,Twinklebear/OSPRay,wilsonCernWq/ospray,favreau/OSPRay,wilsonCernWq/ospray,favreau/OSPRay,favreau/OSPRay,wilsonCernWq/ospray,MengjiaoH/ospray,Twinklebear/OSPRay,MengjiaoH/ospray,ospray/OSPRay,Twinklebear/OSPRay,ospray/OSPRay