Top-level CMake projects containing no target are not resolved

The following project cannot be initially resolved in QtCreator:

project(hpd NONE)

option(HPD_BUILD_X4_FIRMARE   "Build X4 firmware"   OFF)
option(HPD_BUILD_RPMIN_LIB    "Build rpmin library" OFF)

message("Using toolchain: ${CMAKE_CXX_COMPILER_ID}")

if (HPD_BUILD_RPMIN_LIB )
    add_subdirectory(src/hpd)
endif()

if (HPD_BUILD_X4_FIRMARE)
    add_subdirectory(src/x4_firmware)
endif()

Qt Creator claims that resolving was not successful, while the CMake output indicates that everything was OK. I expect this project to be resolved, no matter what kind of toolchain I select and I expect QtCreator to present me the configuration options declared at the top of the file.