Give lldb a clean null build.
Give lldb a clean null build.

`ninja lldb` used to always run "echo -n", which on OS X results in literally
echoing "-n" to the screen.  Just remove the command from add_custom_target,
then it only adds an alias and `ninja lldb` now reports "no work to do".

Other than that, no intended behavior change.


git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@226233 91177308-0d34-0410-b5e6-96231b3b80d8

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