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# Download and unpack nlohmann_json at configure time
configure_file(CMakeLists.txt.in nlohmann_json-download/CMakeLists.txt)
execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
  WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/nlohmann_json-download )
execute_process(COMMAND ${CMAKE_COMMAND} --build .
  WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/nlohmann_json-download )

# Add nlohmann_json directly to our build. This defines
# the nlohmann_json target.
add_subdirectory(${CMAKE_BINARY_DIR}/nlohmann_json-src
                 ${CMAKE_BINARY_DIR}/nlohmann_json-build
                 EXCLUDE_FROM_ALL)

# Now simply link against nlohmann_json
target_link_libraries(main nlohmann_json::nlohmann_json)