Created attachment 457624 [details, diff] fix to the prefix trouble I'm running a Gentoo prefix install (https://wiki.gentoo.org/wiki/Project:Prefix) and current mesa doesn't merge for me, because some va driver files would be installed outside of the prefix directory. I'm attaching a patch that fixes the situation by adding the EPREFIX variable in the right spot.
Created attachment 457626 [details] emerge --info for completeness
Thanks, applied