Override gcc in stdenv for cross-compiled derivation

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1

I am attempting to create a devshell for cross-compiling programs to RISC-V, but I need a gcc built with enableMultilib = true. I tried to override the gcc version used by stdenv when building my shell by doing this in my flake.nix:

{
  inputs = {
    nixpkgs.url = "nixpkgs";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs =
    { self
    , nixpkgs
    , flake-utils
    , ...
    }:
    flake-utils.lib.eachDefaultSystem (system:
    let
      pkgs = (import nixpkgs { inherit system; }).pkgsCross.riscv64-embedded;
      gcc_multilib = pkgs.wrapCCWith {
        cc = pkgs.gcc.cc.override { enableMultilib = true; };
        bintools = pkgs.wrapBintoolsWith {
          bintools = pkgs.binutils-unwrapped;
          libc = pkgs.newlib;
        };
      };
    in
    {
      devShells.default = (pkgs.mkShell.override { stdenv = (pkgs.overrideCC pkgs.stdenv gcc_multilib); }) {
        # ...
      };
    });
}

But it seems that with this method, it attempts to build gcc with its host platform set to riscv64-none-elf, but as a compiler, it should be set to the actual host system (in my case x86_64-linux) with the target platform set to riscv64-none-elf. As such, the derivation fails to build because gcc does not support riscv64-none-elf as its host platform.

2

I believe you want to pull GCC from pkgsBuildTarget, same for binutils-unwrapped.