added include for static embree library

[pnav]

Hello,

This pull request adds a small section to ospray_macros.cmake to properly include Embree as a static library if it is built statically. This relies on Embree pull request 227.

This has been verified using OSPRay 1.7.x build.

[jeffamstutz]

I promise this is still on our plate to merge....we've been doing more overhauls to our CMake stuff, including having our libraries respect BUILD_SHARED_LIBS more appropriately. I'll make sure this makes it into v2.0....we haven't been doing anything with v1.8.x for a while now, but it's time we get this incorporated so it doesn't get lost!

[mathstuf]

Why does this need to be predicated on whether embree is static or not? Is just using the embree imported target not good enough?

[pnav]

@mathstuf the ospray cmake at the time of this pull request hardcoded libembree.so even when embree was built statically. I understand that the cmake config for ospray has changed considerably in 1.8.x so it might work properly now. My embree static lib fixes have been merged into the embree tree for a while, so the latest there will properly expose the static library for testing with ospray.