Revert of [test] Fix cctest path separators on Windows

test/test262-es6/testcfg.py

Index: test/test262-es6/testcfg.py
diff --git a/test/test262-es6/testcfg.py b/test/test262-es6/testcfg.py
index 49a9b254a09e6475c47573b2562711e890e52a7b..f9e9a3946b7ea1a7a0b427ec5e134d30b115d752 100644
--- a/test/test262-es6/testcfg.py
+++ b/test/test262-es6/testcfg.py
@@ -119,9 +119,8 @@
       files.sort()
       for filename in files:
         if filename.endswith(".js"):
-          fullpath = os.path.join(dirname, filename)
-          relpath = fullpath[len(self.testroot) + 1 : -3]
-          testname = relpath.replace(os.path.sep, "/")
+          testname = os.path.join(dirname[len(self.testroot) + 1:],
+                                  filename[:-3])
           case = testcase.TestCase(self, testname)
           tests.append(case)
     return tests