Using non Cargo specific files in the build environment

[Witcher01]

I set up a Makefile for a project of mine that uses Rust with standard rules, including install. When trying to use make install PREFIX=$out in the installPhase it errors out because there is no such rule, even though I have specified it.
Looking closer, the Makefile doesn't even seem to be copied into the build environment at all, all I see are Cargo.lock, Cargo.toml, src, and target.

How do I work with Makefiles, or any other non-cargo files?
If I can't, what's the reasoning, and what's a workaround? I don't want to force nix onto downstream users as I don't want anyone installing a new package manager to use my software that is not required.

Thanks!

flake.nix:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    crane = {
      url = "github:ipetkov/crane";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    flake-utils.url = "github:numtide/flake-utils";
    rust-overlay = {
      url = "github:oxalica/rust-overlay";
      inputs = {
        nixpkgs.follows = "nixpkgs";
        flake-utils.follows = "flake-utils";
      };
    };
  };

  outputs = { self, nixpkgs, crane, flake-utils, rust-overlay }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          system = system;
          overlays = [ (import rust-overlay) ];
        };

        rustToolchain = pkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile
          ./rust-toolchain.toml;
        lib = crane.lib.${system}.overrideToolchain rustToolchain;

        rss-email = lib.buildPackage {
          VERSION = "test";
          src = ./.;
          nativeBuildInputs = with pkgs; [ ];
          installCargoArtifactsMode = "use-symlink";
          installPhase = ''
            mkdir -p $out
            make install PREFIX=$out
          '';
        };
      in
      {
        packages.default = rss-email;
      }
    );
}

[dpc]

By default, if you don't take care of splitting your build into deps-only + normal (using cargoArtifacts), the crane lib will do it for you and both of these will run your installPhase. Usually such default behavior OK, but here it will not work, as in deps-only build, almost all files/code is missing and make needs them.

https://github.com/ipetkov/crane/blob/master/docs/API.md#optional-attributes-1

[ipetkov]

This is exactly what's happening here! Perhaps buildPackage should automatically clear out installPhase for buildDepsOnly (when cargoArtifacts are not specified) to avoid surprises like this 🤔

[ipetkov]

This should be improved with #297

[Witcher01]

I see, thank you for your help and the prompt reply!

@ipetkov Thank you, too, for clarifying this so quickly!