ci: add cache to audit job (#1175)

* ci: add cache to audit job

* always cache, and skip target

* delete registry too

.github/workflows/audit.yml

@@ -18,9 +18,17 @@ jobs:
         with:
           toolchain: stable
 
+      - name: Enable Rust cache
+        uses: Swatinem/rust-cache@988c164c3d0e93c4dbab36aaf5bbeb77425b2894 # 2.4.0
+        with:
+          cache-targets: false
+          cache-all-crates: true
+          cache-on-failure: true
+
       - name: Install cargo-audit
         run: |
           cargo install cargo-audit --locked
+          rm -rf ~/.cargo/registry || echo "no registry to delete"
 
       - uses: rustsec/audit-check@dd51754d4e59da7395a4cd9b593f0ff2d61a9b95 # v1.4.1
         with: