patch the source code to the ScaFaCoS lib with a proper fix instead of working...

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

if(DOWNLOAD_SCAFACOS)

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

  # create variables to pass our compiler flags along to the subsystem compile

  # need to apply -fallow-argument-mismatch, if the fortran compiler supports it

  include(CheckFortranCompilerFlag)

  check_fortran_compiler_flag("-fallow-argument-mismatch" GNUFortran_ARGUMENT_MISMATCH_FLAG)

  if(GNUFortran_ARGUMENT_MISMATCH_FLAG)

    set(APPEND_Fortran_FLAGS "-fallow-argument-mismatch")

  endif()

  include(CheckCCompilerFlag)

  check_c_compiler_flag("-fcommon" GNUC_NO_EXTERN_MISSING_FLAG)

  if(GNUC_NO_EXTERN_MISSING_FLAG)

    set(APPEND_C_FLAGS "-fcommon")

  endif()

  if(CMAKE_Fortran_FLAGS)

    set(SCAFACOS_Fortran_FLAGS "${CMAKE_Fortran_FLAGS} ${APPEND_Fortran_FLAGS}")

  else()

    set(SCAFACOS_Fortran_FLAGS "${CMAKE_Fortran_${CMAKE_BUILD_TYPE}_FLAGS} ${APPEND_Fortran_FLAGS}")

  endif()

  if(CMAKE_CXX_FLAGS)

    set(SCAFACOS_CXX_FLAGS "${CMAKE_CXX_FLAGS}")

  else()

    set(SCAFACOS_CXX_FLAGS "${CMAKE_CXX_${CMAKE_BUILD_TYPE}_FLAGS}")

  endif()

  if(CMAKE_C_FLAGS)

    set(SCAFACOS_C_FLAGS "${CMAKE_C_FLAGS} ${APPEND_C_FLAGS}")

  else()

    set(SCAFACOS_C_FLAGS "${CMAKE_C_${CMAKE_BUILD_TYPE}_FLAGS} ${APPEND_C_FLAGS}")

  endif()

  # version 1.0.1 needs a patch to compile and linke cleanly with GCC 10 and later.

  file(DOWNLOAD https://download.lammps.org/thirdparty/scafacos-1.0.1-fix.diff ${CMAKE_CURRENT_BINARY_DIR}/scafacos-1.0.1.fix.diff

          EXPECTED_HASH MD5=4baa1333bb28fcce102d505e1992d032)

  include(ExternalProject)

  ExternalProject_Add(scafacos_build

    URL https://github.com/scafacos/scafacos/releases/download/v1.0.1/scafacos-1.0.1.tar.gz

    URL_MD5 bd46d74e3296bd8a444d731bb10c1738

    PATCH_COMMAND patch -p1 < ${CMAKE_CURRENT_BINARY_DIR}/scafacos-1.0.1.fix.diff

    CONFIGURE_COMMAND <SOURCE_DIR>/configure --prefix=<INSTALL_DIR> --disable-doc

                                             --enable-fcs-solvers=fmm,p2nfft,direct,ewald,p3m

                                             --with-internal-fftw --with-internal-pfft

                                             --with-internal-pnfft ${CONFIGURE_REQUEST_PIC}

                                             FC=${CMAKE_MPI_Fortran_COMPILER} FCFLAGS=${SCAFACOS_Fortran_FLAGS}

                                             CXX=${CMAKE_MPI_CXX_COMPILER} CXXFLAGS=${SCAFACOS_CXX_FLAGS}

                                             CC=${CMAKE_MPI_C_COMPILER} CFLAGS=${SCAFACOS_C_FLAGS}

                                             FC=${CMAKE_MPI_Fortran_COMPILER}

                                             CXX=${CMAKE_MPI_CXX_COMPILER}

                                             CC=${CMAKE_MPI_C_COMPILER}

                                             F77=

    BUILD_BYPRODUCTS

      <INSTALL_DIR>/lib/libfcs.a