lc0 builds with `-march=native`, which can lead to `Illegal instruction` on docker hosts

[Simske]

Easiest solution: use old anoth architecture that most machines can run it (e.g. -march=broadwell).

Alternatively: compile multiple versions with different -march, choose on runtime.

-march=native is set in meson.build line 41 in lc0 source

Reference links:

• gcc march documentation

[Simske]

Images are now built for march=ivybridge (see 773e6d1), hopefully this is a common base for most users.

It is also easy to add a new image with other march in config.yml.

If the image doesn't work on a specific machine, please post the system specs.