Android Gradle 9 build failure: Project.exec() removed → CargoKit / irondash_engine_context incompatible

[CAJazzer]

After upgrading my Android toolchain, my Flutter app no longer builds when using Gradle 9.x. The failure appears to come from CargoKit via irondash_engine_context, which is pulled in transitively by super_native_extensions.

Execution failed for task ':irondash_engine_context:cargokitCargoBuildIrondash_engine_context_nativeDebug'.

> Could not find method exec() for arguments [...] 
  on project ':irondash_engine_context' of type org.gradle.api.Project

Gradle 9 removed Project.exec {}, which CargoKit’s Gradle script still uses.
This worked on Gradle 8.x (with deprecation warnings) but now fails hard on 9.x.