Embree 3.14.4 forces user to have TBB CMake files installed

[stephanlachnit]

When loading Embree via CMake, it now calls FIND_PACKAGE(TBB REQUIRED), which was not the case with 3.14.3 and before. While one may need the the TBB library for Embree, this not necessarily mean that the CMake files are installed as well - in distribution development files and libraries are usually separated.

I suspect these three lines added the "regression" in 3.14.3:
6ffcaed#diff-60494b839240fb732695392389f3a1f35a323292b38d568f043538d6514daf5bR52-R54

It would be nice if this could be fixed.