Switch to using shlex.quote()

This isn't ideal on Windows, but subprocess.list2cmdline is
private.

As long as we're using the lit internal shell, the shlex quoting
should work fine.

Author: mstorsjo

libcxx/utils/libcxx/test/params.py

@@ -7,17 +7,13 @@
 # ===----------------------------------------------------------------------===##
 import sys
 import re
-import subprocess
+import shlex
 from pathlib import Path
 
 from libcxx.test.dsl import *
 from libcxx.test.features import _isMSVC
 
 
-def quote(x):
-    return subprocess.list2cmdline([x])
-
-
 _warningFlags = [
     "-Werror",
     "-Wall",
@@ -325,7 +321,7 @@ def getStdFlag(cfg, std):
     Parameter(
         name="executor",
         type=str,
-        default=f"{quote(sys.executable)} {quote(str(Path(__file__).resolve().parent.parent.parent / 'run.py'))}",
+        default=f"{shlex.quote(sys.executable)} {shlex.quote(str(Path(__file__).resolve().parent.parent.parent / 'run.py'))}",
         help="Custom executor to use instead of the configured default.",
         actions=lambda executor: [AddSubstitution("%{executor}", executor)],
     )