ci: install cargo-zigbuild in clippy job

The musl linker wrapper for the fspy_test_bin bindep invokes
cargo-zigbuild, so it must be available.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Boshen

.github/workflows/ci.yml

@@ -57,6 +57,7 @@ jobs:
           components: clippy
 
       - run: rustup target add x86_64-unknown-linux-musl
+      - run: pip install cargo-zigbuild
 
       # --locked: verify Cargo.lock is up to date (replaces the removed `cargo check --locked`)
       - run: cargo clippy --locked --all-targets --all-features -- -D warnings