message: [flatc] Remove an always true condition for flexbuffers
  The condition was unnecessary and Detected by
  PVS-Studio
  V560 A part of conditional expression is always true: !opts.use_flexbuffers. flatc.cpp 438
diff: @@ -435,8 +435,7 @@ int FlatCompiler::Compile(int argc, const char **argv) {
  }
  } else {
  ParseFile(*parser.get(), filename, contents, include_directories);
  - if (!opts.use_flexbuffers && !is_schema &&
  - !parser->builder_.GetSize()) {
  + if (!is_schema && !parser->builder_.GetSize()) {
  // If a file doesn't end in .fbs, it must be json/binary. Ensure we
  // didn't just parse a schema with a different extension.
  Error("input file is neither json nor a .fbs (schema) file: " +
  