message: enable testing for regression tests on Windows
diff: @@ -22,7 +22,7 @@ md failed
  cd build
  del CMakeCache.txt
  -cmake -G "Visual Studio 15 2017 Win64" ..
  +cmake -G "Visual Studio 15 2017 Win64" -DOSPRAY_ENABLE_TESTING=ON ..
  cmake --build . --config Release --target ospray_test_data -- /m /nologo
  cd ..
  