embedded assets of copied assets of library

In my library, I'm trying to embed an inline cssUrl of one of my copied assets but it's not working - the output of the background-image is still relative and not inline.

notifications.scss

.icon-info {
    background-image: url("../../assets/icons/info.svg");
}

package.json

"ngPackage": {
  "$schema": "../node_modules/ng-packagr/ng-package.schema.json",
  "dest": "dist",
  "lib": {
    "entryFile": "src/public-api.ts",
    "cssUrl": "inline"
  },
  "assets": [
    "./src/assets/**/*",
    "./src/services/notifications/notifications.scss"
  ]
}

Any idea how to achieve it?