message: adding addPreprocessor with string arg
diff: @@ -127,6 +127,11 @@ public:
  preprocessors.push_back(preprocessor);
  }
  + void addPreprocessor(const std::string& preProcessorName) {
  + auto preprocessor = ServiceRegistry::instance()->getService<Preprocessor>(preProcessorName);
  + preprocessors.push_back(preprocessor);
  + }
  +
  /**
  * Execute the compilation mechanism on the provided program
  * source kernel code to produce XACC IR that can be executed
  