It is up to you. And, perhaps who you think the buyers will be.
If it is a $1000 bike, then most buyers will go ahead and get the bike tuned up.
If it is a $200 bike, then there will be individuals that want a bike they can ride away on. And, I don't think I would sell a bike in that category with a critical safety issue unless I was expecting it to get a full tuneup anyway.
Anyway, my vote would be to fix it. Perhaps bleed the breaks, and inspect for leakage.