Fixing PlaygroundTransform/placeholder.swift to pass on Windows.

Apparently shlex just always assumes posix=True rather than just doing
the right thing.

Author: plotfi

test/PlaygroundTransform/Inputs/not.py

@@ -7,7 +7,8 @@
     sys.exit(0)
 
 try:
-    subprocess.check_call(shlex.split(sys.argv[1]))
+    isPosix = (sys.platform != "win32")
+    subprocess.check_call(shlex.split(sys.argv[1], posix=isPosix))
     sys.exit(1)
 except subprocess.CalledProcessError as e:
     sys.exit(0)