feat(ci): hopefully speed up ci slightly by using nix flake for the d…

…ev shell (evaluations should be cached better)

.envrc

@@ -2,4 +2,8 @@
 # use nix --arg targetSystem '"aarch64-unknown-linux-gnu"'
 
 # for native compilation:
-use nix
+# use nix
+
+# flake version
+use flake .#default
+# use flake .#aarch64-unknown-linux-musl

.github/workflows/rust.yaml

@@ -47,12 +47,11 @@ jobs:
       - uses: DeterminateSystems/magic-nix-cache-action@main
 
       - name: test
-        run: nix-shell --command "cargo test"
+        run: nix develop -c cargo test
       - name: build
         env:
           TARGET_CC: clang
-        run: nix-shell --arg targetSystem \"${{ matrix.target.rust }}\" --run \
-          "cargo build --target ${{ matrix.target.rust }} --release"
+        run: nix develop .#${{ matrix.target.rust }} -c cargo build --target ${{ matrix.target.rust }} --release
 
       - name: Login to Docker registry
         uses: docker/login-action@343f7c4344506bcbf9b4de18042ae17996df046d # v3

flake.nix

@@ -9,7 +9,8 @@
       {
         devShells = {
           # default = with pkgs; mkShellNoCC { packages = [ protobuf ]; };
-          default = import ./shell.nix { inherit pkgs; };
+          default = import ./shell.nix { inherit nixpkgs pkgs system; targetSystem = system; };
+          aarch64-unknown-linux-musl = import ./shell.nix { inherit nixpkgs pkgs system; targetSystem = "aarch64-unknown-linux-musl"; };
         };
       });
 }

shell.nix

@@ -1,13 +1,14 @@
 { nixpkgs ? fetchTarball "https://github.com/NixOS/nixpkgs/tarball/nixos-23.11"
 , pkgs ? import nixpkgs { config = { }; overlays = [ ]; }
 , targetSystem ? builtins.currentSystem
+, system ? builtins.currentSystem # local system
 }:
 let
   crossPkgs =
-    if targetSystem != builtins.currentSystem then
+    if targetSystem != system then
       import nixpkgs
         {
-          localSystem = builtins.currentSystem;
+          localSystem = system;
           crossSystem = { config = targetSystem; };
         }
     else pkgs;