An outdoor access point might do the trick rather than going through the hassle of setting up a point to point link outdoors.
If that's not an option, I've used wi-fi powerline adaptors with some success. Better than just using repeaters - https://www.tp-link.com/uk/home-networking/powerline/tl-wpa7510-kit/
Separate building requires electrical isolation to meet building regs, that doesn't really lend itself to powerline usually.