Use pkg-config for SDL path instead of hardcoding
Use pkg-config for SDL path instead of hardcoding

This is intended to fix

https://ci.appveyor.com/project/Mikolaj/lambdahack/build/1.0.56#L329

by mimicking

https://github.com/rongcuid/sdl2-ttf/commit/5ec78f83ddda894ca56f2b001ce6718e54ab9bd7

sbidin/sdl2-ttf