[BUG] Build args are not substituted into image.base

[pmengelbert]

Expected Behavior

args:
  BUSYBOX_TAG: 1.36
image:
  base: busybox:${BUSYBOX_TAG}

Actual Behavior

With the above:

error handling requested build target "azlinux3/container": could not resolve base image config: error resolving base image config: docker.io/library/busybox:${BUSYBOX_VERSION}: not found

Steps To Reproduce

No response

Are you willing to submit PRs to contribute to this bug fix?

• Yes, I am willing to implement it.