Bug#1082625: mesa: llvm 19 regression: llvmpipe/lavapipe logs message: '-avx512er' is not a recognized feature for this target (ignoring feature)

[Simon McVittie <smcv@debian.org>]

Source: mesa
Version: 24.2.3-1
Severity: normal
Tags: upstream patch
Forwarded: https://gitlab.freedesktop.org/mesa/mesa/-/issues/11870

Since Mesa moved from LLVM 18 to 19, running programs with the lavapipe
or llvmpipe driver logs these messages, sometimes repeatedly:

> '-avx512er' is not a recognized feature for this target (ignoring feature)
> '-avx512pf' is not a recognized feature for this target (ignoring feature)

In particular this caused a test failure for a validation tool in GTK 4,
which I've worked around in src:gtk4 by running that particular test with
GALLIUM_DRIVER=softpipe for now.

Simple reproducers, with mesa-utils and vulkan-tools installed:

    LIBGL_ALWAYS_SOFTWARE=1 glxgears
    VK_LOADER_DRIVERS_SELECT='lvp*' vkcube

I believe https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31321
should be a solution for this (not verified).

    smcv