petsc: add compile and link flags in lib/petsc/conf/petscvariables

      "--with-precision=${precision}"

      "--with-mpi=${if mpiSupport then "1" else "0"}"

    ]

    ++ lib.optionals (!mpiSupport) [

      "--with-cc=${stdenv.cc}/bin/${if stdenv.cc.isGNU then "gcc" else "clang"}"

      "--with-cxx=${stdenv.cc}/bin/${if stdenv.cc.isGNU then "g++" else "clang++"}"

      "--with-fc=${gfortran}/bin/gfortran"

    ]

    ++ lib.optionals mpiSupport [

      "--CC=mpicc"

      "--with-cxx=mpicxx"

      "--with-fc=mpif90"

      "--with-cc=${lib.getDev mpi}/bin/mpicc"

      "--with-cxx=${lib.getDev mpi}/bin/mpicxx"

      "--with-fc=${lib.getDev mpi}/bin/mpif90"

    ]

    ++ lib.optionals (!debug) [

      "--with-debugging=0"

  enableParallelBuilding = true;

  # Ensure petscvariables contains absolute paths for compilers and flags so that downstream

  # packages relying on PETSc's runtime configuration (e.g. form compilers, code generators)

  # can correctly compile and link generated code

  postInstall = lib.concatStringsSep "\n" (

    map (

      package:

      let

        pname = package.pname or package.name;

        prefix =

          if (pname == "blas" || pname == "lapack") then

            "BLASLAPACK"

          else

            lib.toUpper (builtins.elemAt (lib.splitString "-" pname) 0);

      in

      ''

        substituteInPlace $out/lib/petsc/conf/petscvariables \

          --replace-fail "${prefix}_INCLUDE =" "${prefix}_INCLUDE = -I${lib.getDev package}/include" \

          --replace-fail "${prefix}_LIB =" "${prefix}_LIB = -L${lib.getLib package}/lib"

      ''

    ) finalAttrs.buildInputs

  );

  # This is needed as the checks need to compile and link the test cases with

  # -lpetsc, which is not available in the checkPhase, which is executed before

  # the installPhase. The installCheckPhase comes after the installPhase, so