This is why you shouldn't pave up to a house - it always cracks, every time.
The best way is to leave a 100mm gap then fill it with gravel. Then the rain can get in but it can also seep away and evaporate, and won't be held closely against the building.
But that's not where you are. Definitely do not use sand and cement as suggested above. Then you will cause ratcheting - where the paving expands but has nowhere to expand to, so will crack elsewhere instead, or crack the house.
Doing nothing will probably lead to a damp wall, as it will run down that waterproof painted wall and has nowhere to go and will be held against the building.
The best solution would be to get a wet saw and frame, cut a 100mm gap all around the building, dig out to about 150mm and fill it with 20mm gravel. But this probably isn't the sort of idea you're looking for!
But that probably won't work as it looks like you have a slope towards the house. I'd have put some sort of wall or edging behind that drain, away from the house. But this would require the drain to be further away.
Given that you are where you are, flexible construction sealant is the one adequate solution that doesn't involve lots of work. Use some duct tape as masking to avoid creating a smeared mess.
