add support for armv6l

flake.nix

@@ -2,16 +2,19 @@
   description = "Aerogramme";
 
   inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/master";
+    flake-utils.url = "github:numtide/flake-utils";
+
+    # this patched version of cargo2nix makes easier to use clippy for building
     cargo2nix = {
       type = "github";
       owner = "Alexis211";
       repo = "cargo2nix";
       ref = "custom_unstable";
     };
-    nixpkgs.url = "github:NixOS/nixpkgs/master";
+
-    #cargo2nix.url = "github:cargo2nix/cargo2nix/release-0.11.0";
+    # use rust project builds 
     fenix.url = "github:nix-community/fenix/monthly";
-    flake-utils.url = "github:numtide/flake-utils";
   };
 
   outputs = { self, nixpkgs, cargo2nix, flake-utils, fenix }: 
@@ -20,13 +23,32 @@
       "aarch64-unknown-linux-musl"
       "armv6l-unknown-linux-musleabihf"
     ] (targetHost: let
+    
+    # with fenix, we get builds from the rust project.
+    # they are done with an old version of musl (prior to 1.2.x that is used in NixOS),
+    # however musl has a breaking change from 1.1.x to 1.2.x on 32 bit systems.
+    # so we pin the lib to 1.1.x to avoid recompiling rust ourselves.
+    muslOverlay = self: super: {
+      musl = super.musl.overrideAttrs(old: if targetHost == "armv6l-unknown-linux-musleabihf" then rec {
+        pname = "musl";
+        version = "1.1.24";
+        src = builtins.fetchurl {
+          url    = "https://musl.libc.org/releases/${pname}-${version}.tar.gz";
+          sha256 = "sha256:18r2a00k82hz0mqdvgm7crzc7305l36109c0j9yjmkxj2alcjw0k";
+        };
+      } else {});
+    };
+
     pkgs = import nixpkgs { 
       system = "x86_64-linux"; # hardcoded as we will cross compile
       crossSystem = {
         config = targetHost; # here we cross compile
         isStatic = true;
       };
-      overlays = [cargo2nix.overlays.default];
+      overlays = [
+        cargo2nix.overlays.default
+        muslOverlay
+      ];
     };
 
     shell = pkgs.mkShell {
@@ -34,15 +56,17 @@
         cargo2nix.packages.x86_64-linux.default
       ];
     };
+
+    rustTarget = if targetHost == "armv6l-unknown-linux-musleabihf" then "arm-unknown-linux-musleabihf" else targetHost;
     
     rustPkgs = pkgs.rustBuilder.makePackageSet({
+      packageFun = import ./Cargo.nix;
+      target = rustTarget;
       rustToolchain = with fenix.packages.x86_64-linux; combine [
         minimal.cargo
         minimal.rustc
-        targets.${targetHost}.latest.rust-std
+        targets.${rustTarget}.latest.rust-std
       ];
-
-      packageFun = import ./Cargo.nix;
     });
 
     in {