Make the assignment of TestBase.mydir more portable.

llvm-svn: 140640
diff --git a/lldb/test/python_api/lldbutil/frame/TestFrameUtils.py b/lldb/test/python_api/lldbutil/frame/TestFrameUtils.py
index 068077b..04d398b 100644
--- a/lldb/test/python_api/lldbutil/frame/TestFrameUtils.py
+++ b/lldb/test/python_api/lldbutil/frame/TestFrameUtils.py
@@ -9,7 +9,7 @@
 
 class FrameUtilsTestCase(TestBase):
 
-    mydir = "python_api/lldbutil/frame"
+    mydir = os.path.join("python_api", "lldbutil", "frame")
 
     def setUp(self):
         # Call super's setUp().