build: add github action

.github/workflows/nix-github-actions.yml

@@ -0,0 +1,33 @@
+name: Nix Flake actions
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - main
+
+jobs:
+  nix-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v24
+      - id: set-matrix
+        name: Generate Nix Matrix
+        run: |
+          set -Eeu
+          matrix="$(nix eval --json '.#githubActions.matrix')"
+          echo "matrix=$matrix" >> "$GITHUB_OUTPUT"
+
+  nix-build:
+    needs: nix-matrix
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix: ${{fromJSON(needs.nix-matrix.outputs.matrix)}}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v24
+      - run: nix build -L ".#${{ matrix.attr }}"

flake.nix

@@ -2,10 +2,13 @@
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
 
+    nix-github-actions.url = "github:nix-community/nix-github-actions";
+    nix-github-actions.inputs.nixpkgs.follows = "nixpkgs";
+
     utils.url = "github:numtide/flake-utils";
   };
 
-  outputs = { self, nixpkgs, ... } @inputs: inputs.utils.lib.eachSystem [
+  outputs = { self, nixpkgs, nix-github-actions, ... } @inputs: inputs.utils.lib.eachSystem [
     "x86_64-linux" "aarch64-linux" "aarch64-darwin" "x86_64-darwin"
   ] (system: let 
   pkgs = import nixpkgs {
@@ -20,6 +23,10 @@
     });
   };
   in {
+    githubActions = nix-github-actions.lib.mkGithubMatrix { checks = self.packages; };
+    packages.x86_64-linux.hello = nixpkgs.legacyPackages.x86_64-linux.hello;
+    packages.x86_64-linux.default = self.packages.x86_64-linux.hello;
+
     hydraJobs."tester" = self.defaultPackage;
     # hydraJobs."tester-container" = self.container;