Module runner 

Spawn-side companions to super::thin_build::build_obj_plan and super::link_plan::build_link_plan.

Two stages, one helper that wires them together:

• run_obj_plan — invoke rustc with an ObjBuildPlan and return the path of the emitted object file.
• run_link_plan — invoke the linker driver with a LinkPlan and return the path of the produced .so / .dylib.
• thin_rebuild_obj — composes both: build the obj plan, spawn rustc, build the link plan, spawn the linker, return the dylib path.

All three inherit stdout/stderr so compile / link errors land in the dev-server’s terminal instead of being swallowed.

Functions

run_link_plan

Spawn the linker driver with plan.args from cwd. On success, returns the path of the produced shared object (= plan.output).

run_obj_plan

Spawn rustc with plan.args from cwd. On success, returns the path of the emitted object (= plan.expected_object).

thin_rebuild_obj

Compose run_obj_plan and run_link_plan into the full hot-patch rebuild.