postinstall: remove shell=True

Remove the use of shell=True.

src/utils/postinstall.py

@@ -10,6 +10,7 @@ import subprocess
 import shutil
 import logging
 import hivex
+import shlex
 from src.log import OgError
 from src.utils.bcd import update_bcd
 from src.utils.probe import *
@@ -90,19 +91,19 @@ def set_linux_hostname(disk, partition, name):
 
 
 def configure_os_custom(disk, partition):
-    if not shutil.which('configureOsCustom'):
+    command_path = shutil.which('configureOsCustom')
+    if not command_path:
         raise OgError('configureOsCustom not found')
 
     logging.info(f'Found configureOsCustom script, invoking it...')
 
-    cmd_configure = f"configureOsCustom {disk} {partition}"
+    cmd_configure = f"{command_path} {disk} {partition}"
 
     try:
-        proc = subprocess.run(cmd_configure,
+        proc = subprocess.run(shlex.split(cmd_configure),
                               stdout=subprocess.DEVNULL,
                               stderr=subprocess.DEVNULL,
                               encoding='utf-8',
-                              shell=True,
                               check=True)
         out = proc.stdout
     except OSError as e: