rustPlatform.buildRustPackage: infinite recursion on aarch64-darwin with sysroot

[n8henrie]

Describe the bug

On aarch64-darwin, I get an infinite recursion error when trying to use sysroot (by setting a custom rustc target).

I do not get this infinite recursion error on x86_64-linux.

Not sure if related to #180771, but this has popped up a few times for me in the context of nix + rust + darwin => infinite recursion.

Discovered trying to work on #327136.

Steps To Reproduce

Example flake / repo: https://github.com/n8henrie/nix-rust-debug-info/tree/d4d3ee33b380d1f91ec7754201cbb63cf052fa6f

In short,

1. rustc +nightly -Z unstable-options --print target-spec-json > target.json
2. Remove "is-builtin": true, from target.json.
3. Build a rust project with

let
  pkgs = import nixpkgs {
    system = "aarch64-darwin";
    crossSystem = {
      system = "aarch64-darwin";
      rust.rustcTargetSpec = ./target.json;
    };
  };
in
pkgs.callPackage ./. { };

Notify maintainers

I'm unclear if I can just mention a team like this or not:

@NixOS/rust

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"aarch64-darwin"`
 - host os: `Darwin 23.5.0, macOS 14.5`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.18.5`
 - channels(n8henrie): `""`
 - channels(root): `""`
 - nixpkgs: `/nix/store/h5m0sr1l5cwqga83zfdm7qbbrnm1iill-source`

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