[lldb] Fix crash when launching in terminal

[JDevlieghere]

Summary

This patch fixes a crash when using process launch -t to launch the inferior from a TTY. The issue is that on Darwin, Host.mm is calling ConnectionFileDescriptor::Connect without a socket_id_callback_type. The overload passes nullptr as the function ref, which gets called unconditionally as the socket_id_callback. One potential way to fix this is to change all the lambdas to include a null check, but instead I went with a NOOP.

The patch doesn't include a test even though it's trivial to write one. The reason is that we really don't want the test suite spawning (and leaving around) Terminal.app instances on every run.

[labath]

One could add a unit test for the CFD overload, though, as this appears to be the only callsite (or other callsites were equally untested and broken), we could also remove it altogether.

lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp

 }
 
 bool ConnectionFileDescriptor::IsConnected() const {
   return m_io_sp && m_io_sp->IsValid();
 }
 
 ConnectionStatus ConnectionFileDescriptor::Connect(llvm::StringRef path,
                                                    Status *error_ptr) {
-  return Connect(path, nullptr, error_ptr);
+  return Connect(
+      path, [](llvm::StringRef) {}, error_ptr);
 }
 
 ConnectionStatus
 ConnectionFileDescriptor::Connect(llvm::StringRef path,
                                   socket_id_callback_type socket_id_callback,
                                   Status *error_ptr) {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   Log *log = GetLog(LLDBLog::Connection);