Update tesseract.perf.cc

[noajshu]

got these warnings building on macos:

src/tesseract.perf.cc:51:29: warning: compound assignment to object of volatile-qualified type 'volatile size_t' (aka 'volatile unsigned long') is deprecated [-Wdeprecated-volatile] total_num_errors_used += decoder.predicted_errors_buffer.size(); ^ src/tesseract.perf.cc:87:3: note: in instantiation of function template specialization 'benchmark_decoder<TesseractDecoder>' requested here benchmark_decoder(decoder, circuit, num_shots); ^ src/tesseract.perf.cc:51:29: warning: compound assignment to object of volatile-qualified type 'volatile size_t' (aka 'volatile unsigned long') is deprecated [-Wdeprecated-volatile] total_num_errors_used += decoder.predicted_errors_buffer.size(); ^ src/tesseract.perf.cc:108:3: note: in instantiation of function template specialization 'benchmark_decoder<SimplexDecoder>' requested here benchmark_decoder(decoder, circuit, num_shots); ^ 2 warnings generated. INFO: From Linking src/tesseract_perf:

fair enough and we don't need volatile because the cout is a side effect. I sort of wish there were a language feature for not optimizing out variables in C++...