[0.18.0][BugFix]: order acl graph updates before model forward for ENPU (#8317)

<!--  Thanks for sending a pull request!

BEFORE SUBMITTING, PLEASE READ
https://docs.vllm.ai/en/latest/contributing/overview.html

-->
### What this PR does / why we need it?
<!--
- Please clarify what changes you are proposing. The purpose of this
section is to outline the changes and how this PR fixes the issue.
If possible, please consider writing useful notes for better and faster
reviews in your PR.

- Please clarify why the changes are needed. For instance, the use case
and bug description.

- Fixes #
-->
For the ENPU scenario, it is required that device events follow the
principle of "record first, wait later", otherwise the inference process
may become stuck. However, in the current model_forward function,
event.wait precedes event.record. Therefore, for the ENPU scenario,
graph parameter updates should be performed before model execution.

### Does this PR introduce _any_ user-facing change?
<!--
Note that it means *any* user-facing change including all aspects such
as API, interface or other behavior changes.
Documentation-only updates are not considered user-facing changes.
-->
N/A

### How was this patch tested?
<!--
CI passed with new added/existing test.
If it was tested in a way different from regular unit tests, please
clarify how you tested step by step, ideally copy and paste-able, so
that other reviewers can test and check, and descendants can verify in
the future.
If tests were not added, please describe why they were not added and/or
why it was difficult to add.
-->

---------

Signed-off-by: 1zzk <785396250@qq.com>
Signed-off-by: 1kzk <785396250@qq.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

vllm_ascend/utils.py

@@ -1353,3 +1353,21 @@ def parse_layer_idx(prefix: str) -> int | None:
     """Extract the layer index from a module prefix string like 'model.layers.0.self_attn'."""
     match = re.search(r"layers\.(\d+)", prefix)
     return int(match.group(1)) if match else None
+
+
+@lru_cache(maxsize=1)
+def _libc_getenv():
+    import ctypes
+
+    libc = ctypes.CDLL(None)
+    libc.getenv.argtypes = [ctypes.c_char_p]
+    libc.getenv.restype = ctypes.c_char_p
+    return libc.getenv
+
+
+def get_c_env(name: str, encoding: str = "utf-8") -> str | None:
+    """Read env via C getenv; returns None if unset."""
+    raw = _libc_getenv()(name.encode(encoding))
+    if raw is None:
+        return None
+    return raw.decode(encoding)