Debugger: Disable QVariant(KeySequence) dumper for LLDB

This triggers errors in LLDB
  error: main.o Parsing a die that is being parsed die:
      0x00001ddf: DW_TAG_subprogram operator void *QMetaObject::Connection::*
  error: main.o Parsing a die that is being parsed die:
      0x000100fa: DW_TAG_subprogram operator QObjectData *QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> >::*

Change-Id: Iae6a8ca1fbd84c43c7d31b65e017792d1b6a1e0b
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>