[3.14] pythongh-140170: Fix test_site with -s flag (pythonGH-140179) (python#140198)

pythongh-140170: Fix test_site with -s flag (pythonGH-140179)

Commit
(cherry picked from commit 7ac94fc)

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Author: miss-islington

Lib/test/test_site.py

@@ -846,12 +846,15 @@ def get_excepted_output(self, *args):
             return 10, None
 
     def invoke_command_line(self, *args):
-        args = ["-m", "site", *args]
+        cmd_args = []
+        if sys.flags.no_user_site:
+            cmd_args.append("-s")
+        cmd_args.extend(["-m", "site", *args])
 
         with EnvironmentVarGuard() as env:
             env["PYTHONUTF8"] = "1"
             env["PYTHONIOENCODING"] = "utf-8"
-            proc = spawn_python(*args, text=True, env=env,
+            proc = spawn_python(*cmd_args, text=True, env=env,
                                 encoding='utf-8', errors='replace')
 
         output = kill_python(proc)