This requires ISPC for building OpenImageDenoise, so that is now added as
a dependency as well. Blender itself does not need ISPC for building so it
is not included as part of the precompiled libraries.
Differential Revision: https://developer.blender.org/D7641
Reduce the number of possible locations used to find libraries,
to simplify troubleshooting.
Only keep '*_ROOT_DIR' and the path used by 'install_deps.sh'.