[MISC] Make vllm version configurable (#651)

Sometimes, user install a dev/editable version of vllm. In this case, we
should make sure vllm-ascend works as well.

This PR add a new env `VLLM_VERSION`. It's used for developers who edit
vllm. In this case, developers should set thie env to make sure which
vllm version is installed and used.

Signed-off-by: wangxiyuan <wangxiyuan1007@gmail.com>

vllm_ascend/envs.py

@@ -59,7 +59,9 @@ env_variables: Dict[str, Callable[[], Any]] = {
     "CXX_COMPILER":
     lambda: os.getenv("CXX_COMPILER", None),
     "C_COMPILER":
-    lambda: os.getenv("C_COMPILER", None)
+    lambda: os.getenv("C_COMPILER", None),
+    "VLLM_VERSION":
+    lambda: os.getenv("VLLM_VERSION", None),
 }
 
 # end-env-vars-definition