Cog throws "unknown flag: --load" error when buildx isn't installed

[jessie-young]

When buildx isn't installed, running cog commands such as cog predict throws an error unknown flag --load.

Either have cog output a more user-friendly error, or there might be some other fix. Thread from slack:

Thread, for context:
sylvie
maybe we could introspect to find out if buildx is installed

marcus
26 minutes ago
I think just checking for docker buildx version should be enough

sylvie
25 minutes ago
I don't think we used to require it to be installed, though I'm not sure if RUN --mount is a thing outside buildx

jessie.young
19 minutes ago
@sylvie
i manually checked using docker builedx version to see if it was installed after i installed docker, and it wasn’t

sylvie
18 minutes ago
I mean, before we added --load to deal with the GHA thing, I don't believe buildx was required

[zeke]

cc @EduarteXD I think this might be a regression from the related PRs we merged recently.

[EduarteXD]

cc @EduarteXD I think this might be a regression from the related PRs we merged recently.

The load flag was removed in #1656, consider merging it and replicate/setup-cog#36.

This flag was intended to solve the problem of passing products in instances of buildx, which is no longer needed.