lit/TestRunner.py: [Win32] Introduce WinWaitReleased(f), to wait for file handles to be released by children.
lit/TestRunner.py: [Win32] Introduce WinWaitReleased(f), to wait for file handles to be released by children.

When wait() has finished, opened handles (especially writing stdout to file) might not be released immediately.
To wait for released, poll to attempt renaming.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@145222 91177308-0d34-0410-b5e6-96231b3b80d8

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