the arm64 image is trying to use the amd64 version of buildx

[speedarius]

Hi, I noticed this while debugging that we were sometimes seeing this warning in our drone build logs (and subsequently erroring on unknown flag: --rm):

+ docker info
Client:
 Version:    28.1.1
WARNING: Plugin "/root/.docker/cli-plugins/docker-buildx" is not valid: failed to fetch metadata: fork/exec /root/.docker/cli-plugins/docker-buildx: exec format error
 Context:    default
 Debug Mode: false
 Plugins:
  compose: Docker Compose (Docker Inc.)
    Version:  v2.36.2
    Path:     /usr/local/libexec/docker/cli-plugins/docker-compose 

The root cause seems to be at https://github.com/drone-plugins/drone-buildx/blob/master/docker/docker/Dockerfile.linux.arm64#L9C1-L10C101 . It should be pulling the arm64 version of buildx, but is pulling the amd64 version.

I tried to make a pull request, but I don't seem to have permissions to create a branch :)