message: cmake: update DL IE detection to align with OpenVINO 2018 R2
  These CMake options are enough:
  `-DWITH_INF_ENGINE=ON`
  `-DIE_PLUGINS_PATH=lib/ubuntu_16.04/intel64`
  `-DENABLE_CXX11=ON` (OpenCV 3.4 only)
diff: @@ -16,25 +16,27 @@ macro(ie_fail)
  endmacro()
  if(NOT HAVE_CXX11)
  + message(WARNING "DL Inference engine requires C++11. You can turn it on via ENABLE_CXX11=ON CMake flag.")
  ie_fail()
  endif()
  +ocv_check_environment_variables(INTEL_CVSDK_DIR INF_ENGINE_ROOT_DIR IE_PLUGINS_PATH)
  +
  if(NOT INF_ENGINE_ROOT_DIR OR NOT EXISTS "${INF_ENGINE_ROOT_DIR}/include/inference_engine.hpp")
  set(ie_root_paths "${INF_ENGINE_ROOT_DIR}")
  - if(DEFINED ENV{INTEL_CVSDK_DIR})
  - list(APPEND ie_root_paths "$ENV{INTEL_CVSDK_DIR}")
  - list(APPEND ie_root_paths "$ENV{INTEL_CVSDK_DIR}/inference_engine")
  - endif()
  if(DEFINED INTEL_CVSDK_DIR)
  - list(APPEND ie_root_paths "${INTEL_CVSDK_DIR}")
  - list(APPEND ie_root_paths "${INTEL_CVSDK_DIR}/inference_engine")
  + list(APPEND ie_root_paths "${INTEL_CVSDK_DIR}/")
  + list(APPEND ie_root_paths "${INTEL_CVSDK_DIR}/deployment_tools/inference_engine")
  endif()
  if(NOT ie_root_paths)
  - list(APPEND ie_root_paths "/opt/intel/deeplearning_deploymenttoolkit/deployment_tools/inference_engine")
  + list(APPEND ie_root_paths "/opt/intel/computer_vision_sdk/deployment_tools/inference_engine/")
  endif()
  find_path(INF_ENGINE_ROOT_DIR include/inference_engine.hpp PATHS ${ie_root_paths})
  + if(INF_ENGINE_ROOT_DIR MATCHES "-NOTFOUND$")
  + unset(INF_ENGINE_ROOT_DIR CACHE)
  + endif()
  endif()
  set(INF_ENGINE_INCLUDE_DIRS "${INF_ENGINE_ROOT_DIR}/include" CACHE PATH "Path to Inference Engine include directory")
  @@ -43,6 +45,7 @@ if(NOT INF_ENGINE_ROOT_DIR
  OR NOT EXISTS "${INF_ENGINE_ROOT_DIR}"
  OR NOT EXISTS "${INF_ENGINE_ROOT_DIR}/include/inference_engine.hpp"
  )
  + message(WARNING "DL IE: Can't detect INF_ENGINE_ROOT_DIR location.")
  ie_fail()
  endif()
  @@ -50,19 +53,19 @@ set(INF_ENGINE_LIBRARIES "")
  set(ie_lib_list inference_engine)
  +if(NOT IS_ABSOLUTE "${IE_PLUGINS_PATH}")
  + set(IE_PLUGINS_PATH "${INF_ENGINE_ROOT_DIR}/${IE_PLUGINS_PATH}")
  +endif()
  +
  link_directories(
  - ${INTEL_CVSDK_DIR}/inference_engine/external/mkltiny_lnx/lib
  - ${INTEL_CVSDK_DIR}/inference_engine/external/cldnn/lib
  + ${INF_ENGINE_ROOT_DIR}/external/mkltiny_lnx/lib
  + ${INF_ENGINE_ROOT_DIR}/external/cldnn/lib
  )
  foreach(lib ${ie_lib_list})
  - find_library(${lib}
  - NAMES ${lib}
  - # For inference_engine
  - HINTS ${IE_PLUGINS_PATH}
  - HINTS "$ENV{IE_PLUGINS_PATH}"
  - )
  + find_library(${lib} NAMES ${lib} HINTS ${IE_PLUGINS_PATH})
  if(NOT ${lib})
  + message(WARNING "DL IE: Can't find library: '${lib}'")
  ie_fail()
  endif()
  list(APPEND INF_ENGINE_LIBRARIES ${${lib}})
  