USER-SCAFACOS.cmake: fix build with ninja

  endif()

  option(DOWNLOAD_SCAFACOS "Download ScaFaCoS library instead of using an already installed one" ${DOWNLOAD_SCAFACOS_DEFAULT})

  if(DOWNLOAD_SCAFACOS)

    if(CMAKE_GENERATOR STREQUAL "Ninja")

      message(FATAL_ERROR "Cannot build downloaded ScaFaCoS library with Ninja build tool")

    endif()

    message(STATUS "ScaFaCoS download requested - we will build our own")

    include(ExternalProject)

    ExternalProject_Add(scafacos_build

                                               CXX=${CMAKE_MPI_CXX_COMPILER}

                                               CC=${CMAKE_MPI_C_COMPILER}

                                               F77=

      BUILD_BYPRODUCTS 

        <INSTALL_DIR>/lib/libfcs.a

        <INSTALL_DIR>/lib/libfcs_direct.a

        <INSTALL_DIR>/lib/libfcs_ewald.a

        <INSTALL_DIR>/lib/libfcs_fmm.a

        <INSTALL_DIR>/lib/libfcs_p2nfft.a

        <INSTALL_DIR>/lib/libfcs_p3m.a

        <INSTALL_DIR>/lib/libfcs_near.a

        <INSTALL_DIR>/lib/libfcs_gridsort.a

        <INSTALL_DIR>/lib/libfcs_resort.a

        <INSTALL_DIR>/lib/libfcs_redist.a

        <INSTALL_DIR>/lib/libfcs_common.a

        <INSTALL_DIR>/lib/libfcs_pnfft.a

        <INSTALL_DIR>/lib/libfcs_pfft.a

        <INSTALL_DIR>/lib/libfcs_fftw3_mpi.a

        <INSTALL_DIR>/lib/libfcs_fftw3.a

    )

    ExternalProject_get_property(scafacos_build INSTALL_DIR)

    set(SCAFACOS_BUILD_DIR ${INSTALL_DIR})