Draft: TEST REQUEST: temp/mesa: test with LTO enabled

DO NOT MERGE.

Please test Mesa3D builds with LTO (~5% smaller size; 5-15% better CPU-bound performance).

Please report issues here or in the https://gitlab.freedesktop.org/mesa/mesa/-/issues/?sort=created_date&state=opened&label_name%5B%5D=LTO

If you're unsure, ping @okias (on Matrix as David Heidelberg) or @craftyguy