ci: fix clippy (#616)

.github/workflows/clippy.yml

@@ -22,7 +22,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-
+      # cross build failed after Rust 1.68, see https://github.com/cross-rs/cross/issues/1222
+      - run: rustup default 1.67.0
       - uses: Swatinem/rust-cache@v2
         with:
           workspaces: userspace/ksud