Self-host M3: JIT unit probe strict — inventory compile_driver (retire jit_unit_probe_m3_emit_native_entry)

[PurHur]

Milestone

M3 (emit honesty) — parent #1492. Last open slice of #2879 / #3024. Implementation spec: #3038 (script wiring).

Problem

With BOOTSTRAP_M3_USE_INVENTORY_EMIT_DRIVER=1, HelloWorld, compiler-unit, compile-smoke, and runtime-smoke strict probes link inventory compile_driver.php only. JIT unit strict still links jit_unit_probe_m3_emit_native_entry.php (2026-05-28 probe):

bootstrap-selfhost-jit-unit-probe: native emit helper link OK (
  /compiler/build/selfhost-jit-unit-probe-emit,
  selfhost M3 emit TU (jit_unit_probe_m3_emit_native_entry.php))
bootstrap-selfhost-jit-unit-probe: OK emit_path=native …

Probe is green but not honest — duplicate emit TU blocks #3032.

Scope

Path	Work
script/bootstrap-selfhost-jit-unit-probe.sh	Add USE_INVENTORY_EMIT_DRIVER + INVENTORY_EMIT_DRIVER branch (copy from bootstrap-selfhost-compiler-unit-probe.sh)
test/selfhost/jit_unit_probe/compile_driver.php	Ensure exists; set PHP_COMPILER_M3_SOURCE to jit_unit_probe_compile.php
Makefile	bootstrap-selfhost-jit-unit-probe-strict sets BOOTSTRAP_M3_USE_INVENTORY_EMIT_DRIVER=1 (parity with helloworld target)
lib/JIT.php	shouldUseM3InventoryEmitDriver() if probe env must be read at link time

Out of scope: deleting jit_unit_probe_m3_emit_native_entry.php until this is green (#3032).

Repro

./script/docker-exec.sh -- bash -lc '
  BOOTSTRAP_M3_USE_INVENTORY_EMIT_DRIVER=1 \
  BOOTSTRAP_M3_JIT_UNIT_PROBE_STRICT=1 \
  make bootstrap-selfhost-jit-unit-probe-strict 2>&1 | grep -E "inventory|emit_native_entry"
'

Done when

• Log line contains inventory compile_driver (no emit-helper TU
• emit_path=native unchanged (regression: jit unit probe compile OK)
• #3038 closed; this issue closable

[PurHur]

Queued from #1492 backlog-architect run 2026-05-28 — M0–M4 ladder green; north-star5 vendor cold-boot is first red compile-path gate.

[PurHur]

Consolidated into #3038 (implementation spec). 2026-05-29 probe: BOOTSTRAP_M3_USE_INVENTORY_EMIT_DRIVER=1 strict JIT probe still links jit_unit_probe_m3_emit_native_entry.php — PR #3040 in flight.