make ci better

thanks getchoo :3

.github/workflows/build.yml

@@ -1,31 +1,11 @@
-name: build overlay
+name: build packages
 
 on:
   push:
 
 jobs:
-  eval:
-    name: eval flake
-    runs-on: ubuntu-latest
-
-    outputs:
-      matrix: ${{ steps.eval.outputs.matrix }}
-
-    steps:
-      - uses: actions/checkout@v4
-      - uses: DeterminateSystems/nix-installer-action@v9
-
-      - name: evaluate packages
-        id: eval
-        run: echo "matrix=$(nix eval --json .#ghaMatrix)" >> "$GITHUB_OUTPUT"
-
   build:
-    needs: eval
-    strategy:
-      matrix: ${{ fromJson(needs.eval.outputs.matrix) }}
-
-    name: build ${{ matrix.pkg }}
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v4
@@ -38,4 +18,6 @@ jobs:
           authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
 
       - name: build
-        run: nix build -L --accept-flake-config .#${{ matrix.pkg }}
+        run: |
+          nix run --inputs-from . --override-input nixpkgs nixpkgs github:Mic92/nix-fast-build -- \
+            --no-nom --skip-cached --option accept-flake-config true --flake '.#hydraJobs'

ci.nix

@@ -1,45 +1,11 @@
 {
   self,
-  inputs,
+  lib,
   ...
 }: {
-  perSystem = {
-    lib,
-    pkgs,
-    system,
-    ...
-  }: {
-    packages = let
-      overlay = lib.fix (final: (import ./exprs/overlay.nix final pkgs));
-
-      # do not include a package if it's not available on the system or if it's broken
-      isValid = _: v:
-        lib.elem pkgs.system (v.meta.platforms or [pkgs.system]) && !(v.meta.broken or false);
-    in
-      lib.filterAttrs isValid overlay;
+  flake.hydraJobs = let
+    mapCfgsToDerivs = lib.mapAttrs (_: cfg: cfg.activationPackage or cfg.config.system.build.toplevel);
+  in {
+    nixosConfigurations = mapCfgsToDerivs self.nixosConfigurations;
   };
-
-  flake.ghaMatrix.include = let
-    inherit (inputs.nixpkgs) lib;
-
-    platforms = {
-      "x86_64-linux" = {
-        os = "ubuntu-latest";
-      };
-    };
-  in
-    lib.pipe platforms [
-      builtins.attrNames # get systems
-      (systems: lib.getAttrs systems self.packages) # get packages of each system
-      (lib.mapAttrs (_: builtins.attrNames)) # keep only the name of each package
-
-      # map each package in each system to an attrset
-      (lib.mapAttrsToList (system:
-        builtins.map (pkg: {
-          inherit (platforms.${system}) os;
-          pkg = "packages.${system}.${pkg}";
-        })))
-
-      lib.flatten
-    ];
 }