First, we need to install allr required libraries:  
`sudo pacman -S python-numpy vtk hdf5 openmp opencv cuda cudnn`  
It installs all requirements to work with the GPU and the OpenCv's support to Darknet and other libraries; `hdf5` is required to work with `opencv` in `python`; `vtk` is required to compile `Darknet`.  
By default `Darknet` handles libraries' references on `Debian`s based linux systems, then, it requires `opencv`'s as well as `cuda` references to work; in `ArchLinux`, `opencv` is in its `4.1.0` and it used `opencv4` as environment variable, we need change the reference then:  
`sudo cp /usr/lib/pkgconfig/opencv4.pc /usr/lib/pkgconfig/opencv.pc`.  
While the `cuda` library is installed in a different folder than `Debian`'s based systems, we need to created a symbolic link to solve this problem:  
`sudo ln -s /opt/cuda/ /usr/local/cuda`.