NoTarget.cmake
add_library(iface INTERFACE)
target_sources(iface INTERFACE $<TARGET_OBJECTS:NoTarget>)
file(GENERATE OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/test_output CONTENT $<TARGET_OBJECTS:NoTarget>)
file(GENERATE OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/test_output2 CONTENT $<TARGET_PROPERTY:iface,INTERFACE_SOURCES>)
install(FILES $<TARGET_OBJECTS:NoTarget> DESTINATION objects)