add (transparently, cmake advanced option) the old method of setting compiler
add (transparently, cmake advanced option) the old method of setting compiler

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