Build in CI with --locked

This ensures the Cargo.lock file stays up to date. If someone add or
change a dependency in a way that require lockfile changes, the CI
should fail. When the lockfile is versioned it has to stay up to date

.github/workflows/build-and-test.yml

@@ -29,7 +29,7 @@ jobs:
           default: true
 
       - name: Build
-        run: cargo build --all-targets
+        run: cargo build --all-targets --locked
 
       - name: Test
         # Since the tests modify global state (the system firewall) they cannot run in parallel.