Build Embree tutorial.

Former-commit-id: de0a0cdd4f933b2dd0baeca06bd6d63c294448d7

tutorial/CMakeLists.txt

@@ -13,6 +13,7 @@ find_package(MOSEK)
 option(LIBIGL_USE_STATIC_LIBRARY "Use LibIGL as static library" ON)
 option(LIBIGL_WITH_VIEWER      "Use OpenGL viewer"  ON)
 option(LIBIGL_WITH_NANOGUI     "Use Nanogui menu"   OFF)
+option(LIBIGL_WITH_EMBREE      "Use Embree"         ON)
 
 ### libIGL options: choose your dependencies (by default everything is OFF, in this example we need the viewer)
 option(LIBIGL_WITH_CGAL             "Use CGAL"           "${CGAL_FOUND}")