Fallback to amd64 image on mac

[anacierdem]

Currently we publish arm64 images manually and it is sometimes forgotten. When it doesn't exist, libdragon init fails with a docker: no matching manifest for linux/arm64/v8 in the manifest list entries..
When this happens, we can try to fallback to the amd64 image via the --platform linux/amd64 docker flag automatically.

[preland]

I second this