sched_getaffinity() is a Linux specific system call. add preprocessor guards

  }

  }

  #if defined(_LMP_INTEL_LRT_PTHREAD)

  #if defined(_LMP_INTEL_LRT_PTHREAD)

  #if defined(__linux)

  if (comm->me == 0) {

  if (comm->me == 0) {

    cpu_set_t cpuset;

    cpu_set_t cpuset;

    sched_getaffinity(0, sizeof(cpuset), &cpuset);

    sched_getaffinity(0, sizeof(cpuset), &cpuset);

    int my_cpu_count = CPU_COUNT(&cpuset);

    int my_cpu_count = CPU_COUNT(&cpuset);

    if (my_cpu_count < comm->nthreads + 1) {

    if (my_cpu_count < comm->nthreads + 1) {

      char str[128];

      char str[128];

      sprintf(str,"Using %d threads per MPI, but only %d core(s) allocated"

      sprintf(str,"Using %d threads per MPI rank, but only %d core(s)"

                  " per MPI",

                  " allocated for each MPI rank",

              comm->nthreads + 1, my_cpu_count);

              comm->nthreads + 1, my_cpu_count);

      error->warning(FLERR, str);

      error->warning(FLERR, str);

    }

    }

  }

  }

  #endif

  _kspace_ready = 0;

  _kspace_ready = 0;

  _kspace_done = 0;

  _kspace_done = 0;