[lldb] Silence compiler warnings from 37cbd817

lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp:3638:30: error: moving a temporary object prevents copy elision [-Werror,-Wpessimizing-move]
    return SendErrorResponse(std::move(ret.takeError()));
                             ^
lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp:3638:30: note: remove std::move call here
    return SendErrorResponse(std::move(ret.takeError()));
                             ^~~~~~~~~~               ~
lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerLLGS.cpp:3622:8: error: unused variable 'cf' [-Werror,-Wunused-variable]
  bool cf = packet_str.consume_front("qSaveCore");