fix: update subprocess shell handling for cross-platform compatibility

Author: Pavan-Microsoft

scripts/post_deploy.py

@@ -38,18 +38,12 @@
 import base64
 import json
 import os
-import platform
 import subprocess
 import sys
 from dataclasses import dataclass
 from pathlib import Path
 from typing import Dict, Optional
 
-# shell=True is required on Windows so the shell can resolve az.cmd/az.ps1;
-# on Linux/macOS az is a real executable so shell=True must NOT be used with
-# a list argument (it would cause only the first token to be executed).
-_SHELL = platform.system() == "Windows"
-
 try:
     import httpx
 except ModuleNotFoundError as exc:
@@ -122,7 +116,7 @@ def get_values_from_az_deployment(resource_group: str) -> Optional[Dict[str, str
             capture_output=True,
             text=True,
             check=True,
-            shell=_SHELL
+            shell=(os.name == "nt")  # Required on Windows to find az.cmd
         )
         deployment_name = result.stdout.strip()
 
@@ -139,7 +133,7 @@ def get_values_from_az_deployment(resource_group: str) -> Optional[Dict[str, str
                 capture_output=True,
                 text=True,
                 check=True,
-                shell=_SHELL
+                shell=(os.name == "nt")  # Required on Windows to find az.cmd
             )
             deployment_name = result.stdout.strip()
 
@@ -162,7 +156,7 @@ def get_values_from_az_deployment(resource_group: str) -> Optional[Dict[str, str
             capture_output=True,
             text=True,
             check=True,
-            shell=_SHELL
+            shell=(os.name == "nt")  # Required on Windows to find az.cmd
         )
 
         outputs = json.loads(result.stdout)