games-strategy/openra-20170902 from https://github.com/cerebrum/dr/tree/master/games-strategy/openra builds and runs fine for me.
You can improve the .ebuild and discuss it on our support channels https://www.gentoo.org/support/ and make a PR https://wiki.gentoo.org/wiki/Gentoo_Github
openra-20180102.ebuild is out.
Compiles and runs fine here.
Created attachment 517340 [details] openra-20171014.ebuild I tried to build 20171014 as this is most recent stable version https://github.com/OpenRA/OpenRA/releases and bump of an ebuild from portage would not work due to changes in available DOCs. Simple changes there made it work again.
Ebuilds from cerebrum's repo (link in my first comment) work just fine.
I really don't understand Gentoo's strategy here - keep shipping old, buggy, slow and completely obsolete versions while ignoring new, working ebuilds.
*** This bug has been marked as a duplicate of bug 582942 ***