ci: fix magic-nix-cache write permissions

.github/workflows/build.yml

@@ -9,12 +9,17 @@ jobs:
         qtver: [qt6.9.2, qt6.9.1, qt6.9.0, qt6.8.3, qt6.8.2, qt6.8.1, qt6.8.0, qt6.7.3, qt6.7.2, qt6.7.1, qt6.7.0, qt6.6.3, qt6.6.2, qt6.6.1, qt6.6.0]
         compiler: [clang, gcc]
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      id-token: write
     steps:
       - uses: actions/checkout@v4
       # Use cachix action over detsys for testing with act.
       # - uses: cachix/install-nix-action@v27
       - uses: DeterminateSystems/nix-installer-action@main
       - uses: DeterminateSystems/magic-nix-cache-action@main
+        with:
+          use-flakehub: false
 
       - name: Download Dependencies
         run: nix-build --no-out-link --expr '((import ./ci/matrix.nix) { qtver = "${{ matrix.qtver }}"; compiler = "${{ matrix.compiler }}"; }).unwrapped.inputDerivation'