Use customized prebuildify-cross

The official prebuildify-cross always will try to pull the image from ghcr.io even if it exists in the local docker repo.
Instead, we should modify our fork:
  https://github.com/MayamaTakeshi/prebuildify-cross
to check if the image already exists and if yes, to use it.
This will avoid the need to push images to ghcr.io.
