re-enable lldb-mi for the OS X Xcode build (#14)
re-enable lldb-mi for the OS X Xcode build (#14)

* re-enable lldb-mi, with fix for CustomSwift* configurations.

fixes:
rdar://25618608

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb