tests: Fix zero-copy tests (#2498)

.github/workflows/reusable-tests.yaml

@@ -403,7 +403,7 @@ jobs:
             path: tests/declare-id
           - cmd: cd tests/typescript && anchor test --skip-lint && npx tsc --noEmit
             path: tests/typescript
-          - cmd: cd tests/zero-copy && anchor test --skip-lint && cd programs/zero-copy && cargo test-bpf
+          - cmd: cd tests/zero-copy && rustup toolchain install 1.66.1-x86_64-unknown-linux-gnu && anchor test --skip-lint && cd programs/zero-copy && cargo test-bpf
             path: tests/zero-copy
           - cmd: cd tests/chat && anchor test --skip-lint
             path: tests/chat

tests/zero-copy/rust-toolchain.toml

@@ -0,0 +1,3 @@
+# TODO: Remove when `cargo-test-sbf` works with stable Rust
+[toolchain]
+channel = "1.66.1-x86_64-unknown-linux-gnu"