.github/workflows: cache droidctl

.github/workflows/emulator.yml

@@ -36,8 +36,22 @@ jobs:
           name: nix-on-droid
           signingKey: "${{ secrets.CACHIX_SIGNING_KEY }}"
 
-      - name: Build droidctl
-        run: nix build 'github:t184256/droidctl' --out-link droidctl
+      - name: Configure droidctl evaluation cache
+        uses: actions/cache@v4
+        id: droidctl-cache
+        with:
+          path: /tmp/droidctl
+          key: avd-${{ matrix.api-level }}-${{ matrix.way}}  # concurrent save
+
+      - name: Build droidctl (anew and push to cachix)
+        if: steps.droidctl-cache.outputs.cache-hit != 'true'
+        run: |
+          nix build 'github:t184256/droidctl' --out-link /tmp/droidctl
+          realpath /tmp/droidctl | cachix push nix-on-droid
+
+      - name: Fetch droidctl (from cachix using cached eval)
+        if: steps.droidctl-cache.outputs.cache-hit == 'true'
+        run: nix build /tmp/droidctl
 
       - name: Build zipball, channel tarball and flake to inject
         run: |
@@ -92,7 +106,7 @@ jobs:
             cd tests/emulator &&
             adb shell settings put secure enabled_accessibility_services com.google.android.marvin.talkback/com.google.android.marvin.talkback.TalkBackService &&
             echo 'ready' &&
-            nix run 'github:t184256/droidctl' -- run ${{ matrix.way }}.py
+            /tmp/droidctl/bin/droidctl run ${{ matrix.way }}.py
             # TODO: push to cachix from within the emulator
 
       - name: Upload screenshots