let pkgsCrossM68k = import inputs.nixpkgs { system = "x86_64-linux"; cross-system = "m68k-unknown-none-elf"; }; in pkgs.mkShell { ... packages = [ pkgsCrossM68k.stdenv.cc ]; }

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

  outputs =
    inputs:
    inputs.flake-utils.lib.eachDefaultSystem (
      system:
      let
        pkgs = inputs.nixpkgs.legacyPackages.${system};
        pkgsCrossM68k = import "/home/stephen/src/k900/nixpkgs" {
          system = "x86_64-linux"; cross-system = "m68k-unknown-none-elf";
        };
      in
        {
          devShells.default = pkgs.mkShell {
            packages = (
              with pkgs; [
                minipro
                gnumake
                xxd

                pkgsCrossM68k.stdenv.cc
              ]
            );
          };
        }
    );
}

I'm doing nix develop --impure for now. I'll fix the path once things are good

Okay so it seems to be installed! Ty again!
I am unable to use it though. This may not be related to NixOS but I am pretty sure I used this build command on Arch (w/ a custom cross compiler) without issue

m68k-unknown-none-elf-gcc -T Linker.ld -o os.bin -O2 -m68000 -Wall -Wextra -nostdlib start.o main.o -fno-PIE drivers/screen.o drivers/serial.o cpu/interrupt.o cpu/interrupts.o libc/stdlib.o libc/string.o prog/mandelbrot.o prog/memtest.o prog/tty.o   -ffreestanding `m68k-unknown-none-elf-gcc -m68000 -print-libgcc-file-name -ffreestanding`

/nix/store/fmdkz68rg2al0ds776246wkzc12kva5q-m68k-unknown-none-elf-binutils-2.40/bin/m68k-unknown-none-elf-ld: main.o: in function `kmain':
main.c:(.text+0x6): undefined reference to `_GLOBAL_OFFSET_TABLE_'
/nix/store/fmdkz68rg2al0ds776246wkzc12kva5q-m68k-unknown-none-elf-binutils-2.40/bin/m68k-unknown-none-elf-ld: cpu/interrupt.o: in function `error_handler':
interrupt.c:(.text+0x2e): undefined reference to `__stack_chk_guard'

In reply to @stephen:crabsin.space
The assembler does work though FYI (:

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

  outputs =
    inputs:
    inputs.flake-utils.lib.eachDefaultSystem (
      system:
      let
        pkgs = inputs.nixpkgs.legacyPackages.${system};
        pkgsCrossM68k = import "/home/stephen/src/k900/nixpkgs" {
          system = "x86_64-linux"; crossSystem = "m68k-unknown-none-elf";
        };
      in
        {
          devShells.default = pkgs.mkShell {
            packages = (
              with pkgs; [
                minipro
                gnumake
                xxd

                pkgsCrossM68k.stdenv.cc
              ]
            );

            hardeningDisable = ["all"];
          };
        }
    );
}

This is what my flake.nix looks like now but I'm still getting the same errors when building

I am not sure if this helps or not, but I also tried the following:

	/nix/store/ix4mrsayc4i5d61ar59fh1p33nkxchqv-m68k-unknown-none-elf-gcc-13.2.0/bin/m68k-unknown-none-elf-gcc -T Linker.ld -o os.bin -O2 -m68000 -Wall -Wextra -nostdlib start.o main.o -fno-PIE ${OBJ} -ffreestanding `/nix/store/ix4mrsayc4i5d61ar59fh1p33nkxchqv-m68k-unknown-none-elf-gcc-13.2.0/bin/m68k-unknown-none-elf-gcc -m68000 -print-libgcc-file-name -ffreestanding`

I think this skips the wrapper, but I'm still getting the same error messages

I did

bat /nix/store/9j1jlb4921jrl730rlxjk0sba7d415ni-m68k-unknown-none-elf-gcc-wrapper-13.2.0/bin/m68k-unknown-none-elf-gcc

Which had the following: 28 │ [[ "/nix/store/ix4mrsayc4i5d61ar59fh1p33nkxchqv-m68k-unknown-none-elf-gcc-13.2.0/bin/m68k-unknown-none-elf-gcc" = *++ ]] && isCxx=1 || isCxx=0

So I stole the path from there