0.5.2

• Track the impellerc binary as a build input, so bundles rebuild whenever the engine artifacts change.
• Write an engine stamp beside each bundle, so a shared pub-cache bundle rewritten by another project (or Flutter SDK) triggers a rebuild instead of shipping a wrong-engine bundle.
• Recover depfile dependency paths containing spaces (impellerc writes them unescaped); a split path declared a nonexistent dependency, which made the hook re-run on every build for SDKs under paths like Application Support.