How do I substitue version into url path for kustomization

[alita-moore]

Is it possible to use a variable for the version in a kustomization url string?

For example:

resources:
  - https://download.elastic.co/downloads/eck/${version}/crds.yaml

If I use the postBuild option it gives me an error:

apiVersion: kustomize.toolkit.fluxcd.io/v1beta2
kind: Kustomization
metadata:
  name: elastic-crds
  namespace: flux-system
spec:
  interval: 10m0s
  path: ./infra/elastic/crds/overlays/local
  prune: true
  wait: true
  sourceRef:
    kind: GitRepository
    name: monorepo
  postBuild:
    substituteFrom:
      - kind: ConfigMap
        name: elastic-cloud-operator-version

outputs:

kustomize build failed: accumulating resources: accumulation err='accumulating resources from '../../base': read /tmp/kustomization-2571913250/infra/elastic/crds/base: is a directory': recursed accumulation of path '/tmp/kustomization-2571913250/infra/elastic/crds/base': accumulating resources: accumulation err='accumulating resources from 'https://download.elastic.co/downloads/eck/${version}/crds.yaml': URL is a git repository': failed to run '/usr/bin/git fetch --depth=1 https://download.elastic.co/downloads/eck HEAD': fatal: repository 'https://download.elastic.co/downloads/eck/