Better validation when we think a directory might be Xcode.app.
Better validation when we think a directory might be Xcode.app.

LLDB could otherwise get confused if it is (for example) in a
root that is meant to install into an Xcode.app but hasn't
been installed yet.  That way Xcode can fall back to the real
Xcode.app rather than trying to look for resources inside the
root.


git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@252198 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb