message: Use concrete MPI version
diff: @@ -69,7 +69,7 @@ option(BUILD_OSPRAY_CI_TESTS "Enable OSPRay's tests." OFF)
  option(BUILD_OSPRAY_CI_EXTRAS "Enable OSPRay's extra compiler checks." OFF)
  option(BUILD_OSPRAY_MODULE_MPI "Enable fetch/build of module_mpi" OFF)
  -set(BUILD_OSPRAY_MODULE_MPI_VERSION "devel" CACHE STRING "What version of module_mpi?")
  +set(BUILD_OSPRAY_MODULE_MPI_VERSION "v2.1.0" CACHE STRING "What version of module_mpi?")
  option(INSTALL_IN_SEPARATE_DIRECTORIES
  "Install libraries into their own directories under CMAKE_INSTALL_PREFIX"
  