Install openfortivpn on 19.07


I have Linksys WRT3200ACM with OpenWRT 19.07. My company is using Fortigate. I would like to connect to company network using openfortivpn. As I can see there is openfortivpn package ( but is available only in version 21. How I can install it on 19.07?
Is available any option to use FortiVPN on OpenWRT 19.07?

Best regards