In the case that the prefix is `/usr`, system wlroots headers installed in `/usr/include/wlr` will be preferred over those bundled by hyprland as `-I` directories are searched [from left to right](https://gcc.gnu.org/onlinedocs/cpp/Search-Path.html), which is not great since the system wlroots headers might not be compatible with hyprland. Fix the order of cflags so bundled wlroots headers will be preferred over system ones.
