Compiling OpenFOAM

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Greetings!

I’m trying to compile OpenFOAM on NixOS using a flake.nix file + it’s corresponding shell.

{
  description = "OpenFOAM Compilation env";

  inputs.nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0"; # stable Nixpkgs

  outputs =
    { self, ... }@inputs:

    let
      supportedSystems = [
        "x86_64-linux"
        "aarch64-linux"
        "x86_64-darwin"
        "aarch64-darwin"
      ];
      forEachSupportedSystem =
        f:
        inputs.nixpkgs.lib.genAttrs supportedSystems (
          system:
          f {
            pkgs = import inputs.nixpkgs { inherit system; };
          }
        );
    in
    {
      devShells = forEachSupportedSystem (
        { pkgs }:
        {
          default =
            pkgs.mkShell.override
              {
                # Override stdenv in order to change compiler:
                # stdenv = pkgs.clangStdenv;
              }
              {
                packages =
                  with pkgs;
                  [
                    flex
                    gnum4
                    gcc
                    clang-tools
                    clang
                    cmake
                    codespell
                    conan
                    cppcheck
                    doxygen
                    gtest
                    lcov
                    vcpkg
                    vcpkg-tool
                    openmpi
                    file
                  ]
                  ++ (if system == "aarch64-darwin" then [ ] else [ gdb ]);
                shellHook = ''
                  source ./etc/bashrc

                  # Ensure OpenFOAM finds m4
                  PATH=${pkgs.gnum4}/bin:$PATH

                  # Ensure m4 include paths exist
                  M4PATH=$WM_PROJECT_DIR:$WM_PROJECT_DIR/src:$WM_PROJECT_DIR/src/OpenFOAM
                '';
              };
        }
      );
    };
}

To compile I’m using:

./Allmake -s -l

It works out until it errors out with:

make -f /home/bm69/git/third_party/openFoam/OpenFOAM-v2412/wmake/makefiles/general 'MAKE_DIR=Make' 'OBJECTS_DIR=/home/bm69/git/third_party/openFoam/OpenFOAM-v2412/build/linux64GccDPInt32Opt/src/OpenFOAM' libso
    lyy-m4too: fieldExprLemonParser.lyy-m4
    lemon-m4: fieldExprLemonParser.lyy-m4
m4:expressions/fields/fieldExprLemonParser.lyy-m4:96: cannot open `fieldExprLemonParserMacros.m4': No such file or directory
m4:expressions/fields/fieldExprLemonParser.lyy-m4:425: cannot open `[m4/lemon/parser-methods.m4]': No such file or directory
m4 stage failed on expressions/fields/fieldExprLemonParser.lyy-m4

This seems to be a simple path error, but I’m not smart enough to figure out how to set m4 search path in this context (setting the variable M4PATH as noticed in the m4 documentation doesn’t seem to work.
Has anybody encountered this?

Thanks in advance!