Update contrib/building.md
Update contrib/building.md

Adding NVM to the guide

Co-authored-by: Kræn Hansen <5562fc2b794a5d0371171401ae9222ba0e4551a1@mongodb.com>
realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js,realm/realm-js