quality.yml: generate Cargo.lock before audit step

rustsec/audit-check requires a Cargo.lock at the working directory.
Our stubs gitignore Cargo.lock (since it's a published-as-stub crate
that won't get its lockfile committed). Add a `cargo generate-lockfile`
step in CI so audit has something to scan.

Author: dcharlot65-openie

.github/workflows/quality.yml

@@ -51,6 +51,11 @@ jobs:
         run: |
           DIR=$(find stubs -mindepth 1 -maxdepth 1 -type d | head -1)
           echo "dir=$DIR" >> "$GITHUB_OUTPUT"
+      - name: Generate Cargo.lock
+        if: steps.stub.outputs.dir
+        working-directory: ${{ steps.stub.outputs.dir }}
+        run: cargo generate-lockfile
+
       - name: Audit
         if: steps.stub.outputs.dir
         uses: rustsec/audit-check@v2.0.0