CI: test magic nix cache action

Author: algorithmiker

.github/workflows/test.yml

@@ -5,11 +5,13 @@ on:
 jobs:
   tests:
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write
     steps:
     - uses: actions/checkout@v4
-    - uses: cachix/install-nix-action@v31
-      with:
-        nix_path: nixpkgs=channel:nixos-unstable
+    - uses: DeterminateSystems/nix-installer-action@main
+    - uses: DeterminateSystems/magic-nix-cache-action@main
     - run: nix build -v -L .#entrace
     - run: nix build -v -L .#entrace_core
     - run: nix build -v -L .#entrace_core_lite