Fix security audit installation on the ARM64 runner (#122)

.gitea/workflows/security-audit.yml

@@ -16,7 +16,12 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Install the reviewed cargo-audit release
-        run: cargo install cargo-audit --locked --version 0.22.2
+        uses: https://github.com/taiki-e/install-action@9534c84618278caac52cb373bb164ed464dbd8af # v2
+        with:
+          tool: cargo-audit@0.22.2
+          fallback: none
 
       - name: Reject new RustSec vulnerabilities
-        run: cargo audit --ignore RUSTSEC-2023-0071
+        # Invoke the prebuilt binary directly: the runner has no Cargo toolchain.
+        # The existing RSA exception is documented in docs/ssh-transport-audit.md.
+        run: cargo-audit audit --ignore RUSTSEC-2023-0071