ci: enable lint, integration with cache (#103)

## 📝 Summary

- Re-enable linting in CI
- Integration checks using cache should speed up build significantly

---

## ✅ I have completed the following steps:

* [x] Run `make lint`
* [x] Run `make test`
* [x] Added tests (if applicable)

.github/workflows/checks.yaml

@@ -54,8 +54,9 @@ jobs:
         run: sudo apt-get install -y libsqlite3-dev
 
       # lint and test
-      # - run: make lint FIX THIS
+      - run: make lint
       - run: make test
+
   integration:
     name: Integration tests
     runs-on: warp-ubuntu-latest-x64-16x
@@ -75,6 +76,21 @@ jobs:
         with:
           builder-playground: latest
 
+      # https://github.com/swatinem/rust-cache
+      - name: Run Swatinem/rust-cache@v2
+        uses: Swatinem/rust-cache@v2
+        with:
+          cache-on-failure: true
+
+      # https://github.com/Mozilla-Actions/sccache-action
+      - name: Run sccache-action
+        uses: mozilla-actions/[email protected]
+
+      - name: Set sccache env vars
+        run: |
+          echo "SCCACHE_GHA_ENABLED=true" >> $GITHUB_ENV
+          echo "RUSTC_WRAPPER=sccache" >> $GITHUB_ENV
+
       - name: Build the rbuilder
         run: cargo build