chore: get secrets via input, mock for CI

this fixes CI, yay!

.github/workflows/niveum.yml

@@ -10,10 +10,21 @@ jobs:
         system: [makanek,manakish,kabsa,zaatar,ful]
     steps:
     - uses: actions/checkout@v2
-    - uses: cachix/install-nix-action@v16
-    - name: Install nixos-rebuild
-      run: GC_DONT_GC=1 nix-env -i nixos-rebuild -f '<nixpkgs>'
+    - name: Install QEMU (ARM)
+      run: sudo apt-get install -y qemu-user-static
+      if: ${{ matrix.system == 'ful' }}
+    - name: Install Nix (ARM)
+      uses: cachix/install-nix-action@v16
+      if: ${{ matrix.system == 'ful' }}
+      with:
+        extra_nix_config: |
+          system = aarch64-linux
+    - name: Install Nix (x86_64)
+      uses: cachix/install-nix-action@v16
+      if: ${{ matrix.system != 'ful' }}
     - run: |
         rm -rf secrets
         mkdir secrets
-    - run: GC_DONT_GC=1 nixos-rebuild dry-build --flake .#{{matrix.system}}
+        cat secrets.txt | while read -r path; do echo dummy > $path; done
+        find
+    - run: nix run nixpkgs#nixos-rebuild -- dry-build --override-input secrets ./secrets --flake .#${{matrix.system}}