Build can embed the wrong runtime after switching Pulley feature

hyperlight-wasm/build.rs から始め、ネストされた runtime の出力と生成された wasm_runtime_resource.rs が OUT_DIR と共有ターゲットパスをどのように使用しているかを調べます。consumer の normal -\u003e pulley -\u003e normal と pulley -\u003e normal -\u003e pulley のシーケンスを再現し、その後、native ビルドと Pulley ビルドを同時実行します。各 AOT コンポーネントが対応する埋め込み runtime でロードされ、同時実行されるビルドが正しく分離されたままになることが完了条件です。

Summary

Switching between native and Pulley builds can embed the wrong hyperlight-wasm-runtime guest. A native host build can retain the Pulley runtime and reject a valid x86 AOT component:

GuestError(GuestError, "Module was compiled for architecture 'x86_64'")

Reproduction

Use a consumer feature that enables hyperlight-wasm/pulley.

1. Build and run with an x86 AOT component.
2. Build and run with the Pulley feature and a Pulley AOT component.
3. Build and run with the x86 AOT component again.

The third run can reject the x86 component. This reproduces with hyperlight-wasm 0.15.0 and Wasmtime 36.0.14.

Root cause

hyperlight-wasm/build.rs builds the embedded runtime into a shared nested target directory:

<target>/hyperlight-wasm-runtime/x86_64-hyperlight-none/<profile>/hyperlight-wasm-runtime

Native and Pulley Cargo units have separate OUT_DIR directories. Both generated wasm_runtime_resource.rs files use include_bytes! with this shared mutable path.

The nested Pulley build overwrites the runtime binary. Cargo can rebuild the native hyperlight-wasm unit because the include_bytes! input changed while its build script remains cached. The native unit then embeds the Pulley binary.

The shared output also permits a race between concurrent normal and Pulley builds.

Suggested fix

Copy the completed nested runtime into the outer build script's OUT_DIR. Point include_bytes! at that private copy. This preserves the shared nested compilation cache.

Concurrent builds also need one of these protections:

• Hold a lock across the nested build and copy.
• Use a separate nested target directory for each runtime configuration.

The configuration key must cover pulley, gdb, trace_guest, wasmtime_latest, and the WIT environment values. The outer OUT_DIR provides complete isolation but duplicates compilation work.

Regression coverage

Build a consumer in both sequences. Verify that the final component loads:

normal -> pulley -> normal
pulley -> normal -> pulley

Concurrent native and Pulley builds should produce correctly matched embedded runtimes.