Tests/CMakeCommands/target_sources/subdir/CMakeLists.txt

target_sources(target_sources_lib PUBLIC $<1:${CMAKE_CURRENT_LIST_DIR}/subdir_empty_1.cpp>
                                         $<1:${CMAKE_CURRENT_LIST_DIR}/../empty_1.cpp>
                                         subdir_empty_2.cpp
                                  PRIVATE $<1:empty_2.cpp>
                                          ../empty_3.cpp)