This pulls in the s390x fix needed by #3330. Also a small `rsix` API update; `PollFdVec` has been removed in favor of just using `Vec<PollFd>`.
This is the test-programs crate, which builds and runs whole programs
compiled to wasm32-wasi.
To actually run these tests, the test-programs feature must be enabled, e.g.:
cargo test --features test-programs/test_programs --package test-programs