message: Allow users to set the install prefix directory.
diff: @@ -41,6 +41,7 @@ ExternalProject_Add(
  BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/ngraph/build"
  BUILD_COMMAND ${CMAKE_MAKE_PROGRAM} -j $(nproc) ngraph
  UPDATE_COMMAND ""
  + INSTALL_DIR "${CMAKE_INSTALL_PREFIX}"
  )
  set( NGRAPH_DIR ${CMAKE_CURRENT_BINARY_DIR}/ngraph/ngraph_dist)
  @@ -49,7 +50,10 @@ set( NGRAPH_DIR ${CMAKE_CURRENT_BINARY_DIR}/ngraph/ngraph_dist)
  find_package(TensorFlow REQUIRED)
  # Set the Install Prefix, rpath etc. here (cannot be done in the sub directories)
  +if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
  set(CMAKE_INSTALL_PREFIX ${TensorFlow_DIR})
  +endif()
  +MESSAGE("INSTALL DIR: ${CMAKE_INSTALL_PREFIX}")
  # Add the directories to be built
  add_subdirectory(src)
  