Optional dependencies cause build failures when incompatible about nix-cargo-integration HOT 8 CLOSED

error: Package ‘MacOS_SDK-10.12’ in /nix/store/hsff9pi1qinxljahr833z0xivr1apx27-source/pkgs/os-specific/darwin/apple-sdk/default.nix:50 is not supported on ‘x86_64-linux’, refusing to evaluate.
...

❯ NCI_DEBUG=1 nix build --impure
trace: root at: /nix/store/8f9kibyd69lb0kf5pph0hsna8nfa0idq-2h6x3j10r6jkb7i4mik3g8wqsffi2cbh-source
trace: workspace members:
trace: {
  message = "temp-0.1.0: root is";
  value = /nix/store/2h6x3j10r6jkb7i4mik3g8wqsffi2cbh-source;
}
trace:

The dream-lock.json for input 'temp' doesn't exist or is outdated.
...Falling back to on-the-fly evaluation (possibly slow).
To speed up future evalutations run once:
  nix run .#resolve

trace: {
  message = "temp-0.1.0: using builder";
  value = "crane";
}
trace: {
  message = "temp-0.1.0: rawTomlOverrides";
  value = {
    autocfg = <function>;
    bitflags = <function>;
    cc = <function>;
    cfg-if = <function>;
    core-foundation = <function>;
    core-foundation-sys = <function>;
    fastrand = <function>;
    foreign-types = <function>;
    foreign-types-shared = <function>;
    instant = <function>;
    lazy_static = <function>;
    libc = <function>;
    log = <function>;
    native-tls = <function>;
    once_cell = <function>;
    openssl = <function>;
    openssl-probe = <function>;
    openssl-sys = <function>;
    pkg-config = <function>;
    redox_syscall = <function>;
    remove_dir_all = <function>;
    schannel = <function>;
    security-framework = <function>;
    security-framework-sys = <function>;
    temp = <function>;
    temp-deps = <function>;
    tempfile = <function>;
    vcpkg = <function>;
    winapi = <function>;
    winapi-i686-pc-windows-gnu = <function>;
    winapi-x86_64-pc-windows-gnu = <function>;
  };
}
trace: {
  message = "temp-0.1.0: tomlOverrides";
  value = {
    autocfg = <function>;
    bitflags = <function>;
    cc = <function>;
    cfg-if = <function>;
    core-foundation = <function>;
    core-foundation-sys = <function>;
    fastrand = <function>;
    foreign-types = <function>;
    foreign-types-shared = <function>;
    instant = <function>;
    lazy_static = <function>;
    libc = <function>;
    log = <function>;
    native-tls = <function>;
    once_cell = <function>;
    openssl = <function>;
    openssl-probe = <function>;
    openssl-sys = <function>;
    pkg-config = <function>;
    redox_syscall = <function>;
    remove_dir_all = <function>;
    schannel = <function>;
    security-framework = <function>;
    security-framework-sys = <function>;
    temp = <function>;
    temp-deps = <function>;
    tempfile = <function>;
    vcpkg = <function>;
    winapi = <function>;
    winapi-i686-pc-windows-gnu = <function>;
    winapi-x86_64-pc-windows-gnu = <function>;
  };
}
trace: {
  message = "temp-0.1.0: buildPhase";
  value = ''
    runHook preBuild
    echo running: 'cargo build --release --message-format json-render-diagnostics >"$cargoBuildLog"'
    cargoBuildLog=$(mktemp cargoBuildLogXXXX.json)
    cargo build --release --message-format json-render-diagnostics >"$cargoBuildLog"
    runHook postBuild
  '';
}
error: Package ‘MacOS_SDK-10.12’ in /nix/store/hsff9pi1qinxljahr833z0xivr1apx27-source/pkgs/os-specific/darwin/apple-sdk/default.nix:50 is not supported on ‘x86_64-linux’, refusing to evaluate.

       a) To temporarily allow packages that are unsupported for this system, you can use an environment variable
          for a single invocation of the nix tools.

            $ export NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1

        Note: For `nix shell`, `nix build`, `nix develop` or any other Nix 2.4+
        (Flake) command, `--impure` must be passed in order to read this
        environment variable.

       b) For `nixos-rebuild` you can set
         { nixpkgs.config.allowUnsupportedSystem = true; }
       in configuration.nix to override this.

       c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
         { allowUnsupportedSystem = true; }
       to ~/.config/nixpkgs/config.nix.
(use '--show-trace' to show detailed location information)