python312Packages.h5py: use environment to spare mpi4py setup.py substitutions

  pythonRelaxDeps = [ "mpi4py" ];

  # avoid strict pinning of numpy and mpi4py, can't be replaced with

  # pythonRelaxDepsHook, see: https://github.com/NixOS/nixpkgs/issues/327941

  # Avoid strict pinning of Numpy, can't be replaced with pythonRelaxDepsHook,

  # as these are build time dependencies. See:

  # https://github.com/NixOS/nixpkgs/issues/327941

  postPatch = ''

    substituteInPlace pyproject.toml \

      --replace-fail "numpy >=2.0.0, <3" "numpy"

    substituteInPlace setup.py \

      --replace-fail "mpi4py ==3.1.4" "mpi4py" \

      --replace-fail "mpi4py ==4.0.1" "mpi4py" \

      --replace-fail "mpi4py ==3.1.6" "mpi4py"

  '';

  env = {

    HDF5_DIR = "${hdf5}";

    HDF5_MPI = if mpiSupport then "ON" else "OFF";

    # See discussion at https://github.com/h5py/h5py/issues/2560

    H5PY_SETUP_REQUIRES = 0;

  };

  postConfigure = ''