github actions: init

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/build.yml

@@ -0,0 +1,24 @@
+name: "nix-build"
+on:
+  pull_request_target:
+    branches:
+      - 'master'
+  push:
+    branches:
+      - 'master'
+  workflow_dispatch:
+jobs:
+  nix-build:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ ubuntu-latest, macos-latest ]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+    - name: Install Nix
+      uses: DeterminateSystems/nix-installer-action@v12
+    - uses: DeterminateSystems/magic-nix-cache-action@v7
+    - name: Build some-pkgs
+      run: nix run github:Mic92/nix-fast-build -- --skip-cached --no-nom --flake ".#packages"