Failure to build when just enabling Arrows and Tests

[Purg]

With fletch-provided Eigen3:

 CMAKE_BUILD_TYPE                 Debug                                                                                                                                                                                                           
 CMAKE_INSTALL_PREFIX             /usr/local                                                                                                                                                                                                      
 KWIVER_CPP_WERROR                OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_ARROWS             ON                                                                                                                                                                                                              
 KWIVER_ENABLE_CERES              OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_CUDA               OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_C_BINDINGS         OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_EXAMPLES           OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_EXTRAS             OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_FFMPEG             OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_GDAL               OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_LOG4CPLUS          OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_MATLAB             OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_OPENCV             OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_OPENMP             OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_PROJ               OFF                                                                                                                                                                                                              
 KWIVER_ENABLE_QT                 OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_SERIALIZE_JSON     OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_SERIALIZE_PROTOB   OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_SPROKIT            OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_TESTS              ON                                                                                                                                                                                                              
 KWIVER_ENABLE_TOOLS              OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_TRACK_ORACLE       OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_VXL                OFF                                                                                                                                                                                                             
 KWIVER_ENABLE_ZeroMQ             OFF                                                                                                                                                                                                             
 KWIVER_USE_CONFIGURATION_SUBDI   OFF                                                                                                                                                                                                             
 fletch_DIR                       /home/local/KHQ/paul.tunison/dev/fletch/build-master                                                                                                                                                            

After a call to make (filtering to just a call post error so the one error is shown):

...
[ 69%] Built target test-core-triangulate_landmarks
[ 69%] Building CXX object arrows/core/tests/CMakeFiles/test-core-transfer_bbox_with_depth_map.dir/test_transfer_bbox_with_depth_map.cxx.o
/home/local/KHQ/paul.tunison/dev/kwiver/source/arrows/core/tests/test_transfer_bbox_with_depth_map.cxx:37:10: fatal error: opencv2/core/core.hpp: No such file or directory
 #include <opencv2/core/core.hpp>
          ^~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [arrows/core/tests/CMakeFiles/test-core-transfer_bbox_with_depth_map.dir/build.make:63: arrows/core/tests/CMakeFiles/test-core-transfer_bbox_with_depth_map.dir/test_transfer_bbox_with_depth_map.cxx.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1985: arrows/core/tests/CMakeFiles/test-core-transfer_bbox_with_depth_map.dir/all] Error 2
make: *** [Makefile:163: all] Error 2