Add urpmi as an alternative to apt in ./build.sh

[sailinggalaxians]

Running ./build.sh gives me the following error:

Build environment not found in "/home/kristoffer/ubportsdocsenv" ... creating it.
Installing pip and virtualenv (using sudo).
sudo: apt: command not found

I already have pip and python3-virtualenv installed using the offered rpm packages from the official Mageia 8 medias.