flake-test/flake.nix

{
    description = "Fake Flake";

    inputs = {
        nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
        flake-utils.url = "github:numtide/flake-utils";
    };

    outputs = { self, nixpkgs, flake-utils }: flake-utils.lib.eachDefaultSystem (system:
    let
        pkgs = import nixpkgs { inherit system; };
    in {
        packages = rec {
            default = cfile;
            cfile = pkgs.stdenv.mkDerivation {
                name = "hello";
                src = self;
                buildInputs = [
                    pkgs.gcc
                ];
                buildPhase = "gcc -o hello ./hello.c";
                installPhase = "mkdir -p $out/bin; install -t $out/bin hello";
            };

            pdf = let outputFilename = "yolo.pdf";
            in pkgs.stdenv.mkDerivation {
                name = "some-pdf";
                src = self;
                buildInputs = [
                    pkgs.typst
                    cfile
                ];
                buildPhase = ''
                    ${cfile}/bin/hello > dummyfile.typ
                    typst compile dummyfile.typ ${outputFilename}
                '';
                installPhase = "mkdir $out; install -t $out ${outputFilename}";
            };
        };
    });
}