As developer, I do not know/care about builder, I only want to select buildpack strategy to kick off my build, so that is simple for me

[ZhuangYuZY]

Now, in build cr, when I select buildpack as build strategy, I still need to input builder image. It is not good for end user, actually, end user do not need to take care of buildpack image, he just want to consume buildpack capabilities.

apiVersion: build.dev/v1alpha1
kind: Build
metadata:
  name: xxx
spec:
  builder:
    image: heroku/buildpacks:18

So suggest to move the builder image to build strategy cr. When administrator install buildpack strategy, we could select one of buildpack builder.