Print port number that lldb-server binds to in platform mode

[vharron]

Summary

This improves the reliability of platform startup by ensuring that
a free port can be found.

[ovyalov]

LGTM

[vharron]

r238173

tools/lldb-server/lldb-platform.cpp

for (const auto &lldb_command : lldb_commands)
         debugger_sp->GetCommandInterpreter().HandleCommand(lldb_command.c_str(), eLazyBoolNo, result);
         const char *output = result.GetOutputData();
         if (output && output[0])
             puts(output);
     }
 
     std::unique_ptr<Socket> listening_socket_up;
     Socket *socket = nullptr;
-    printf ("Listening for a connection from %s...\n", listen_host_port.c_str());
     const bool children_inherit_listen_socket = false;
 
     // the test suite makes many connections in parallel, let's not miss any.
     // The highest this should get reasonably is a function of the number 
     // of target CPUs.  For now, let's just use 100
     const int backlog = 100;
     error = Socket::TcpListen(listen_host_port.c_str(), children_inherit_listen_socket, socket, NULL, backlog);
     if (error.Fail())
     {
         printf("error: %s\n", error.AsCString());
         exit(socket_error);
     }
     listening_socket_up.reset(socket);
+    printf ("Listening for a connection from %u...\n", listening_socket_up->GetLocalPortNumber());
 
     do {
         GDBRemoteCommunicationServerPlatform platform;
         
         if (port_offset > 0)
             platform.SetPortOffset(port_offset);
 
         if (!gdbserver_portmap.empty())