[Support/LockFileManager] Use symbolic link for the lock file.
[Support/LockFileManager] Use symbolic link for the lock file.

Hard links do not work on SMB network directories, and it causes us to fail
to build clang module files if the module cache is in such a directory.
rdar://15944959

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@203137 91177308-0d34-0410-b5e6-96231b3b80d8

dslab-epfl/asap,dslab-epfl/asap,chubbymaggie/asap,chubbymaggie/asap,GPUOpen-Drivers/llvm,llvm-mirror/llvm,dslab-epfl/asap,chubbymaggie/asap,GPUOpen-Drivers/llvm,apple/swift-llvm,dslab-epfl/asap,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,dslab-epfl/asap,chubbymaggie/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,llvm-mirror/llvm,chubbymaggie/asap,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,chubbymaggie/asap,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,dslab-epfl/asap