[test] Fix & re-enable CommandScriptImmediateOutputFile on Windows

Apparently the shlex module produces garbage on Windows. I've added a
hand rolled split instead that should suffice for this test.

llvm-svn: 358216

lldb/lit/Commands/CommandScriptImmediateOutput/CommandScriptImmediateOutputFile.test

@@ -1,5 +1,3 @@
-# UNSUPPORTED: system-windows
-
 # Test that LLDB correctly allows scripted commands to set immediate output to
 # a file.
 

lldb/lit/Commands/CommandScriptImmediateOutput/Inputs/custom_command.py

@@ -1,16 +1,19 @@
 from __future__ import print_function
 
 import sys
-import shlex
 
 
+def split(command):
+    command = command.strip()
+    return command.rsplit(' ', 1)
+
 def command_function(debugger, command, exe_ctx, result, internal_dict):
     result.SetImmediateOutputFile(sys.__stdout__)
     print('this is a test string, just a test string', file=result)
 
 
 def write_file(debugger, command, exe_ctx, result, internal_dict):
-    args = shlex.split(command)
+    args = split(command)
     path = args[0]
     mode = args[1]
     with open(path, mode) as f: