Transitive dependencies through Cmake External Projects

Question

Is there a way to make an external dependency depend of two others external dependencies of a project ?

Here is my situation

• core depdends on boost_program_options and on quetzal
• quetzal depends on gdal and boost_filesystem and boost_unit_test_framework

How to orchestrate these dependencies ? I have been trying the following approach:

The root CMakelist.txt contains:

list(APPEND BOOST_COMPONENTS_REQUIRED program_options)
add_subdirectory(external/upstream)
    ExternalProject_Add(
      ${PROJECT_NAME}_core
      DEPENDS
        boost_external
        gdal_external
        quetzal_external
      SOURCE_DIR
        ${CMAKE_CURRENT_LIST_DIR}/FTD_core
      CMAKE_ARGS
        -DCMAKE_INSTALL_PREFIX=${STAGED_INSTALL_PREFIX}
        -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
        -DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}
        -DCMAKE_CXX_EXTENSIONS=${CMAKE_CXX_EXTENSIONS}
        -DCMAKE_CXX_STANDARD_REQUIRED=${CMAKE_CXX_STANDARD_REQUIRED}
      CMAKE_CACHE_ARGS
        -DCMAKE_CXX_FLAGS:STRING=${CMAKE_CXX_FLAGS}
        -DCMAKE_LIBRARY_PATH:PATH=${STAGED_INSTALL_PREFIX}
        # Forward externals to the core project
        -DCMAKE_INCLUDE_PATH:PATH=${BOOST_INCLUDEDIR}
        -DCMAKE_LIBRARY_PATH:PATH=${BOOST_LIBRARYDIR}
        -DCMAKE_INCLUDE_PATH:PATH=${GDAL_INCLUDE_DIR}
        -DCMAKE_LIBRARY_PATH:PATH=${GDAL_LIBRARY}
        -DCMAKE_INCLUDE_PATH:PATH=${QUETZAL_INCLUDE_DIR}
      BUILD_ALWAYS
        1
      INSTALL_COMMAND
        ""
      )

The external/upstream/quetzal/CMakeLists.txt contains:

list(APPEND BOOST_COMPONENTS_REQUIRED unit_test_framework filesystem)
      include(ExternalProject)
      ExternalProject_Add(quetzal_external
        DEPENDS
          boost_external
          gdal_external
        GIT_REPOSITORY https://github.com/Becheler/quetzal.git
        GIT_TAG        master
        CMAKE_ARGS
          -DCMAKE_LIBRARY_PATH:PATH=${STAGED_INSTALL_PREFIX}
          -DCMAKE_INCLUDE_PATH:PATH=${BOOST_INCLUDEDIR}
          -DCMAKE_LIBRARY_PATH:PATH=${BOOST_LIBRARYDIR}
          -DCMAKE_INCLUDE_PATH:PATH=${GDAL_INCLUDE_DIR}
          -DCMAKE_LIBRARY_PATH:PATH=${GDAL_LIBRARY}
              -DCMAKE_INSTALL_PREFIX=${CMAKE_CURRENT_BINARY_DIR}
              -DCMAKE_PREFIX_PATH=${CMAKE_CURRENT_BINARY_DIR}
              -DBUILD_TESTS=Off
          UPDATE_COMMAND ""
        )

external/upstream/boost/CMakeLists.txt and external/upstream/gdal/CMakeLists.txt seem to behave adequately. But for some reason external/upstream/quetzal/CMakeLists.txt finds the system boost installation (1.71), when I want it to find the locally built boost installation (1.65).

I think something is wrong with my way to forward the boost dependency to the quetzal dependency, but I don't even know if the general approach is correct or not.