shell.nix

let
  foo = import ./release.nix {};
  c2hs-libical = foo.pkgs.writeShellScriptBin "c2hs-libical" ''
    ${foo.pkgs.haskellPackages.c2hs}/bin/c2hs --cppopts='-I${foo.libical.dev}/include' $1
  '';
in
  foo.build.env.overrideAttrs (drv: {
    CPATH = "${foo.libical.dev}/include";
    buildInputs = (drv.buildInputs or []) ++ [
      foo.libical
      foo.libical.dev
      foo.pkgs.haskellPackages.ghcid
      foo.pkgs.haskellPackages.hpack
      foo.pkgs.haskellPackages.yesod-bin
      foo.pkgs.haskellPackages.c2hs
      c2hs-libical
    ];
  })