message: Add logging when ArchSpec::SetArchitecture is given a cputype and
  cpusubtype that don't map to any known core definition.
  <rdar://problem/39779398>
diff: #include "lldb/Utility/ArchSpec.h"
  +#include "lldb/Utility/Log.h"
  #include "lldb/Utility/NameMatches.h"
  #include "lldb/Utility/Stream.h" // for Stream
  #include "lldb/Utility/StringList.h"
  @@ -978,6 +979,10 @@ bool ArchSpec::SetArchitecture(ArchitectureType arch_type, uint32_t cpu,
  if (m_triple.getArch() == llvm::Triple::UnknownArch)
  m_triple.setArch(core_def->machine);
  }
  + } else {
  + Log *log(lldb_private::GetLogIfAnyCategoriesSet(LIBLLDB_LOG_TARGET | LIBLLDB_LOG_TARGET | LIBLLDB_LOG_PLATFORM));
  + if (log)
  + log->Printf("Unable to find a core definition for cpu 0x%" PRIx32 " sub %" PRId32, cpu, sub);
  }
  }
  CoreUpdated(update_triple);
  