Spawn/exec fixture #

The parent uses the runtime's constrained vfork-style clone, then the child passes data through an inherited blocking-mode pipe before loading /project/spawn/child with execve. The pipe uses O_CLOEXEC, proving that closing the child's copies during execve leaves the suspended parent's copies and queued data intact. The child validates its argument, prints spawned child, and exits 7. The restored parent reaps that exact status with wait4, validates the pipe data and EOF, prints parent resumed, and exits zero.

The filesystem image and both ELFs are deterministic checked-in fixtures. Rebuild them with every cache and temporary file inside the repository:

guest-tests/spawn-exec/build.sh