Fixes the following build failure when building with gcc 11:
478 ../../../../CPP/7zip/Archive/Wim/WimHandler.cpp: In member function 'virtual LONG NArchive::NWim::CHandler::GetArchiveProperty(PROPID, PROPVARIANT*)':
>> 479 ../../../../CPP/7zip/Archive/Wim/WimHandler.cpp:308:11: error: use of an operand of type 'bool' in 'operator++' is forbidden in C++17
480 308 | numMethods++;
481 | ^~~~~~~~~~
>> 482 ../../../../CPP/7zip/Archive/Wim/WimHandler.cpp:318:9: error: use of an operand of type 'bool' in 'operator++' is forbidden in C++17
483 318 | numMethods++;
484 | ^~~~~~~~~~
218b1c153c