message: Fix compiler unused variable warning in DWARFUnit
  Alex Langford has reported it from:
diff: @@ -205,8 +205,6 @@ bool DWARFUnit::ExtractDIEsIfNeeded() {
  // Final checks for both ExtractUnitDIEIfNeeded() and ExtractDIEsIfNeeded().
  //--------------------------------------------------------------------------
  void DWARFUnit::ExtractDIEsEndCheck(lldb::offset_t offset) const {
  - lldb::offset_t next_cu_offset = GetNextCompileUnitOffset();
  -
  // Give a little bit of info if we encounter corrupt DWARF (our offset should
  // always terminate at or before the start of the next compilation unit
  // header).
  