include external targets with relative paths

app/CMakeLists.txt

@@ -3,9 +3,9 @@ if (MSVC)
 else()
     add_compile_options(-Wall -Wextra -Wpedantic -Wconversion -Wno-unused-parameter -Wno-unused-function -fconcepts-diagnostics-depth=4)
 endif()
-include(${CMAKE_SOURCE_DIR}/extern/cli11.cmake)
-include(${CMAKE_SOURCE_DIR}/extern/json.cmake)
-include(${CMAKE_SOURCE_DIR}/extern/magic_enum.cmake)
+include(../extern/cli11.cmake)
+include(../extern/json.cmake)
+include(../extern/magic_enum.cmake)
 add_subdirectory(shapefile_splitter)
 add_subdirectory(sda-workflow)
 add_subdirectory(examples)
\ No newline at end of file