How to et environment = production

[dragGH102]

I managed to adapt this started template to the project I'm currently working on.

Both work correctly:

• gulp serve-dev
• gulp serve-build

However I can't manage to set production environment:

 NODE_ENV=production && gulp serve-build # or NODE_ENV="production" && gulp serve-build

still prints:

Current environment: development
Change environment via --env or NODE_ENV

  gulp serve-dev --env production # or gulp --env production serve-dev

returns this error:

Task 'serve-build' is not in your gulpfile

Any clue?
Thanks in advance