message: Install the Eigen headers
  Install if the Eigen from the submodule (3rdparty directory) is used. This is the case, except when a user specifies their own EIGEN3_INCLUDE_DIR - in that case, we don't want to install the headers.
diff: @@ -141,6 +141,10 @@ install(DIRECTORY ${eos_3RDPARTY_DIR}/nanoflann/include/ DESTINATION 3rdparty/na
  install(FILES ${eos_3RDPARTY_DIR}/nanoflann/COPYING DESTINATION 3rdparty/nanoflann/) # nanoflann licence
  install(DIRECTORY ${eos_3RDPARTY_DIR}/eigen3-nnls/src/ DESTINATION 3rdparty/eigen3-nnls/src) # eigen3-nnls header
  install(FILES ${eos_3RDPARTY_DIR}/eigen3-nnls/README.md DESTINATION 3rdparty/eigen3-nnls/) # eigen3-nnls attribution
  +# Install Eigen headers if we're using the Eigen submodule included with eos:
  +if(EIGEN3_INCLUDE_DIR STREQUAL ${eos_3RDPARTY_DIR}/eigen)
  + install(DIRECTORY ${eos_3RDPARTY_DIR}/eigen/Eigen/ DESTINATION 3rdparty/eigen/Eigen)
  +endif()
  if(EOS_BUILD_EXAMPLES)
  add_subdirectory(examples)
  