nix build now uses cache

.github/workflows/run-builds.yml

@@ -1,16 +1,38 @@
-name: Builds
+name: "nix CI"
-
 on:
   push:
     branches: [master]
   workflow_dispatch:
-
 jobs:
-  build-nix-flake:
+  build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2.3.4
+    - uses: actions/checkout@v3
-      - uses: cachix/install-nix-action@v15
+    - uses: cachix/install-nix-action@v18
-      - run: nix develop -c echo ok
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - id: cache-restore
+      uses: actions/cache/restore@v3
+      with:
+        path: nix-store.nar
+        key: nix-store-nar-${{ hashFiles('flake.lock') }}
+    - if: steps.cache-restore.outputs.cache-hit == 'true'
+      run: |
+        nix-store --import < nix-store.nar
+        rm nix-store.nar
+
+    - run: nix develop
     - run: nix build
     - run: nix build .#clerk
+
+    - name: dump store
+      if: steps.cache-restore.outputs.cache-hit == 'false'
+      run: nix-store --export $(nix-store -qR $(nix print-dev-env --json | jq .variables.prefix.value -r)) > nix-store.nar
+    - name: save current cache
+      if: steps.cache-restore.outputs.cache-hit == 'false'
+      uses: actions/cache/save@v3
+      id: cache
+      with:
+        path: nix-store.nar
+        key: nix-store-nar-${{ hashFiles('flake.lock') }}
+