lib.systems: Add arm-embedded-nano

[RossSmyth]

Newlib-nano variant of the arm-embedded stdenv.

Reasoning:

#385908 was denied because of pkgsCross. But the problem is that the arm-embedded pkgsCross toolchain does not use newlib nano. It would be nice to fill the gap and have a toolchain that is cached that has newlib-nano for embedded developers (like me).

I would prefer that it is a multilib, but it seems the multilib cross toolchains are broken, and an assert was added recently to ensure they aren't added in #380325.

#51907
#111321

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

---

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[RossComputerGuy]

pkgsCross.arm-embedded-nano.stdenv builds fine on aarch64-linux. However, pkgsCross.arm-embedded-nano.hello fails:

hello> checking whether the C compiler works... no
hello> configure: error: in `/build/hello-2.12.1':
hello> configure: error: C compiler cannot create executables
hello> See `config.log' for more details

In config.log:

/nix/store/3v0cyab13cj668v1ywh2ywf9sxh82fzc-arm-none-eabi-binutils-2.43.1/bin/arm-none-eabi-ld: warning: -z relro ignored
/nix/store/3v0cyab13cj668v1ywh2ywf9sxh82fzc-arm-none-eabi-binutils-2.43.1/bin/arm-none-eabi-ld: /nix/store/hrxwq72pyk4pnyprgi4n9a94syh69wqw-newlib-arm-none-eabi-4.5.0.20241231
/arm-none-eabi/lib/libc.a(libc_a-exit.o): in function `exit':
/build/newlib-4.5.0.20241231/arm-none-eabi/newlib/../.././newlib/libc/stdlib/exit.c:65:(.text+0x3c): undefined reference to `_exit'
/nix/store/3v0cyab13cj668v1ywh2ywf9sxh82fzc-arm-none-eabi-binutils-2.43.1/bin/arm-none-eabi-ld: /nix/store/hrxwq72pyk4pnyprgi4n9a94syh69wqw-newlib-arm-none-eabi-4.5.0.20241231
/arm-none-eabi/lib/libc.a(libc_a-closer.o): in function `_close_r':
/build/newlib-4.5.0.20241231/arm-none-eabi/newlib/../.././newlib/libc/reent/closer.c:47:(.text+0x24): undefined reference to `_close'
/nix/store/3v0cyab13cj668v1ywh2ywf9sxh82fzc-arm-none-eabi-binutils-2.43.1/bin/arm-none-eabi-ld: /nix/store/hrxwq72pyk4pnyprgi4n9a94syh69wqw-newlib-arm-none-eabi-4.5.0.20241231
/arm-none-eabi/lib/libc.a(libc_a-lseekr.o): in function `_lseek_r':
/build/newlib-4.5.0.20241231/arm-none-eabi/newlib/../.././newlib/libc/reent/lseekr.c:49:(.text+0x30): undefined reference to `_lseek'
/nix/store/3v0cyab13cj668v1ywh2ywf9sxh82fzc-arm-none-eabi-binutils-2.43.1/bin/arm-none-eabi-ld: /nix/store/hrxwq72pyk4pnyprgi4n9a94syh69wqw-newlib-arm-none-eabi-4.5.0.20241231
/arm-none-eabi/lib/libc.a(libc_a-readr.o): in function `_read_r':
/build/newlib-4.5.0.20241231/arm-none-eabi/newlib/../.././newlib/libc/reent/readr.c:49:(.text+0x30): undefined reference to `_read'
/nix/store/3v0cyab13cj668v1ywh2ywf9sxh82fzc-arm-none-eabi-binutils-2.43.1/bin/arm-none-eabi-ld: /nix/store/hrxwq72pyk4pnyprgi4n9a94syh69wqw-newlib-arm-none-eabi-4.5.0.20241231
/arm-none-eabi/lib/libc.a(libc_a-writer.o): in function `_write_r':
/build/newlib-4.5.0.20241231/arm-none-eabi/newlib/../.././newlib/libc/reent/writer.c:49:(.text+0x30): undefined reference to `_write'
/nix/store/3v0cyab13cj668v1ywh2ywf9sxh82fzc-arm-none-eabi-binutils-2.43.1/bin/arm-none-eabi-ld: /nix/store/hrxwq72pyk4pnyprgi4n9a94syh69wqw-newlib-arm-none-eabi-4.5.0.20241231
/arm-none-eabi/lib/libc.a(libc_a-sbrkr.o): in function `_sbrk_r':
/build/newlib-4.5.0.20241231/arm-none-eabi/newlib/../.././newlib/libc/reent/sbrkr.c:51:(.text+0x24): undefined reference to `_sbrk'
collect2: error: ld returned 1 exit status

[RossSmyth]

When using newlib-nano those symbols are not defined, and are meant to be user-defined (or not defined at all). The use case is generally something like defining them to output to a serial port when building a program for a microcontroller. So that is expected.

[RossSmyth]

I double checked just to make sure, I tested it before with

crossPkgs = import nixpkgs {
    localSystem = pkgs.stdenv.buildPlatform;
    crossSystem = {
        config = "arm-none-eabi";
        libc = "newlib-nano";
    };
};

and pkgsCross.arm-embedded-nano from this PR is able to build the firmware I work on that uses newlib-nano.

[RossSmyth]

nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review pr 392204

---

x86_64-linux

⏩ 2 packages blacklisted:

• nixos-install-tools
• tests.nixos-functions.nixos-test

✅ 1 package built:

• nixpkgs-manual