[DirectoryWatcher] Handle errors returned by close()
[DirectoryWatcher] Handle errors returned by close()

https://reviews.llvm.org/D58418

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang