if(PROJECT_ENABLE_DTL)
  if(PROJECT_BUILD)
    add_definitions(-DPROJECT_ENABLE_DTL)
  else()
    ExternalProject_Add(dtl_project
      PREFIX external
      URL ${PROJECT_3RD_PARTY_DIR}/dtl-v${DTL_VERSION}.tar.gz
      URL_HASH SHA256=d6dcc7834b4117b5c14456ea73b907d0e2bafa5058e3a06b2c504d53517438c5
      LIST_SEPARATOR |
      CMAKE_ARGS ${PROJECT_EXTERNAL_CMAKE_FLAGS}
        -DBUILD_SHARED_LIBS=${PROJECT_BUILD_SHARED_LIBS}
        -DBUILD_STATIC_LIBS=ON
    )

    set(PROJECT_DEPENDENCIES 
      ${PROJECT_DEPENDENCIES}
      dtl_project
    )
  endif()
endif()