Disable an in-memory vfs file path test on windows.
Disable an in-memory vfs file path test on windows.

The test uses unix paths and doesn't make sense to run on windows.

Fix bot failure caused by r333172:
 http://lab.llvm.org:8011/builders/clang-x64-ninja-win7/builds/10799

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@333186 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang