Upvote:4
Apply to the Netherlands for one visa covering both trips. If they decide to grant the visa for just the Netherlands trip, you can then apply to Spain for a visa to cover the Barcelona trip.
I suggest applying to the Netherlands because the job interview arguably makes the Netherlands your main destination when considering the two trips together. However, if you are spending several days in Barcelona, they may decide that Spain should be considered the main destination. In that case, they should reject the application with a suggestion that you apply to Spain for a visa to cover both trips, in which case you should of course do that.