Bug#1015039: gtk4 memorytexture test-case regresses with Mesa 22.1

[Simon McVittie]

Control: reassign -1 src:mesa 22.1.3-1
Control: affects -1 + src:gtk4
Control: forwarded -1 https://gitlab.freedesktop.org/mesa/mesa/-/issues/6898

On Sat, 16 Jul 2022 at 18:16:11 +0100, Simon McVittie wrote:
> I can reproduce this test failure with sid's mesa 22.1.3-1, but not with
> bookworm's mesa, so it seems like this is probably a mesa regression (or
> possibly a mesa behaviour change that means what gtk4 is doing no longer
> works).

I bisected this to mesa commit 6bbbe15a "Reinstate: llvmpipe: allow
vertex processing and fragment processing in parallel" and reported it
upstream: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6898

A straightforward revert of 6bbbe15a applies cleanly to 22.1.x and
appears to solve this.

    smcv