Created attachment 439334 [details] working ebuild libva-vdpau-driver-9999 I am attaching the fixed ebuild to build from upstream correctly libva-vdpau-driver-9999.ebuild
please attach diffs & explain what you changed and what fails
Created attachment 439358 [details, diff] a diff
The problem is your upstream builder doesn't build because the source is flawed, so it needs the three previous patches and also it needs to drop the old autoutils as it creates multiple errors in the configuration files. I used eautoreconf instead of the older autoutils. This ebuild works on multiple platforms as of now. I am sure you don't need a detailed line by line explanation as you are more knowledgeable at this than me.
Please don't mess with the importance fields on your own. There haven't been any commits since the 0.7.4 release, which happened more than four years ago. I've removed the 9999 ebuild in commit e9f23f1dfce2749e9e994c393175b9cbd464faed Author: Matt Turner <mattst88@gentoo.org> Date: Sun Jan 29 10:12:34 2017 -0800 x11-libs/libva-vdpau-driver: Drop live ebuild.