lit.py: Give up and disable the new shared-output.py test on Windows
lit.py: Give up and disable the new shared-output.py test on Windows

"No such file or directory: C:\\...\\tests\\Output\\shared-output.py.tmp/Output/Shared/SHARED.tmp"

And yet other forward-slashes don't seem to be causing the same
problem. I'll see if I can get ahold of a Windows machine to poke at
this directly later.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@315792 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm