* nongnu/packages/mesa.scm (mesa-next)[phases]{fix-instrfromstring-test}: New
phase. Fix the instrfromstring test which fails on i686 using the upstream change.
* nongnu/packages/mesa.scm (libva-without-mesa): New variable. This is
unchanged from Guix, but needed locally for mesa to build.
(mesa-next): New variable. This is copied from mesa on the core-updates branch
of Guix.
