Stdlib: getenv() local_only second argument — VM + AOT (#3710)

[PurHur]

Summary

• Implements getenv(string $name, bool $local_only = false) per php-src zif_getenv / EG(env) — VmEnv tracks putenv() assignments; local_only=true reads only that table.
• Fixes putenv() / getenv() as statements: internal handlers no longer return early when returnVar is null (FUNCCALL_EXEC_NORETURN), which previously made putenv('X=1'); a no-op before a 2-arg getenv() call.
• AOT: phpc_env_local.c, extended __compiler_getenv(name, local_only, out), StringEnvLocal MCJIT bitcode link; putenv JIT registers local table via __compiler_env_register_putenv.

php-src: ext/standard/basic_functions.c

Test plan

• vendor/bin/phpunit --filter getenv_local_only — VMTest + AotTest green
• php bin/compile.php -l test/repro-maintainer/getenv_local_only.php
• JITTest — MCJIT subprocess exit -1 in Docker harness (same class of flake as other getenv/putenv JIT cases); bin/jit.php may segfault on this host — follow-up if needed

Closes #3710

Made with Cursor

[PurHur]

Maintainer review (local Docker)

Verified on `agent/stdlib-getenv-local-only` via `./script/docker-exec.sh`:

• `vendor/bin/phpunit --filter getenv_local_only` — VMTest + AotTest pass (3/5 cases)
• JITTest `stdlib/getenv_local_only*` — MCJIT subprocess exit -1 (same class as other getenv/putenv JIT flakes noted in PR)

Not merging until JIT compliance is green or explicitly scoped VM+AOT-only with JITTest skips documented on #3710.

VM semantics for `local_only` and `putenv` no-return fix look correct from repro; good to land once JIT path is stable or skipped like other env builtins.