Reserve memory for the Units vector

src/main.cpp

@@ -42,6 +42,7 @@ int main(int argc, char* argv[]) {
     if (!files.empty()) {
         vector<future<pair<string, optional<Yerbacon::Exception>>>> Units;
         const launch& Policy = not parallel ? launch::deferred : launch::async;
+        Units.reserve(files.size());
         transform(files.begin(), files.end(), back_inserter(Units), [&Policy, &compile](const string_view& fileName){
             return async(Policy, [&fileName, &compile]() {
                 pair<string, optional<Yerbacon::Exception>> resultingPair;