message: Minor correction concerning compilation compatibility with CUDA 9.0
  Since CUDA 9.0 doesn't support sm_20 and sm_21 anymore. This PR allows Caffe to compile with CUDA 9.0 and newer versions successfully.
  This addresses the discussion concerning [#6237](https://github.com/BVLC/caffe/pull/6237) in [master (#6237)](https://github.com/BVLC/caffe/commit/cb150eca6d593ddb85e53acd05b8dcf709ea8337#diff-2004a3d3e6b4ed2e2812bb0b4b998f18)
diff: @@ -109,8 +109,8 @@ function(caffe_select_nvcc_arch_flags out_variable)
  set(__nvcc_flags "")
  set(__nvcc_archs_readable "")
  - string(COMPARE GREATER_EQUAL "${CUDA_VERSION}" "9.1" iscudanewerthan91)
  - if(iscudanewerthan91)
  + string(COMPARE GREATER_EQUAL "${CUDA_VERSION}" "9.0" iscudanewerthan90)
  + if(iscudanewerthan90)
  string(REPLACE "21(20)" "" __cuda_arch_bin "${__cuda_arch_bin}")
  string(REPLACE "20" "" __cuda_arch_bin "${__cuda_arch_bin}")
  endif()
  