Build can embed the wrong runtime after switching Pulley feature

从 hyperlight-wasm/build.rs 开始，检查嵌套 runtime 输出和生成的 wasm_runtime_resource.rs 如何使用 OUT_DIR 和共享的目标路径。复现 consumer 的 normal -\u003e pulley -\u003e normal 以及 pulley -\u003e normal -\u003e pulley 序列，然后测试并发的 native 和 Pulley 构建。完成的标准是每个 AOT 组件都使用与其匹配的内嵌 runtime 加载，并且并发构建仍能保持正确隔离。

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.