src: merge env-file and env vars of `NODE_OPTIONS`
Follow-up for https://github.com/nodejs/node/issues/49148. Prior to this change, we were preferring the environment variables over .env
file. Right now, we merge them.
Ref: https://github.com/nodejs/node/issues/49148
cc @GeoffreyBooth @ljharb @tniessen @gireeshpunathil