Scala 2.13 immutable-sequences?

[yamin-oanda]

On https://twitter.github.io/scrooge/CommandLine.html#scrooge-generator

It is instructed:

--language-flag Pass arguments to supported language generators. To generate Scala 2.13 compatible scala.Seq alias as scala.collection.immutable.Seq, please use "immutable-sequences".

However it is not clear how exactly to pass in this command-line argument. According to https://twitter.github.io/scrooge/SBTPlugin.html#scrooge-sbt-configuration-options

scroogeBuildOptions: Seq[String]

list of command-line arguments to pass to scrooge (default: Seq(“WithFinagle”))

However this documentation seems incorrect and it seems to have been a Seq[ServiceOption] for a long time now: 5979724?diff=unified&w=0#diff-83e8daaecab09dbc766048e5ea463929ef92658795f3d8669bacea67d85c2417L20

And ServiceOption is locked down so we can't pass in arbitrary strings like --language-flag immutable-sequences:

scrooge/scrooge-generator/src/main/scala/com/twitter/scrooge/backend/Generator.scala

Line 37 in c99132b

abstract sealed class ServiceOption

abstract sealed class ServiceOption

case object WithFinagle extends ServiceOption
case object WithJavaPassThrough extends ServiceOption
case object WithAsClosable extends ServiceOption {
  val AsClosableMethodName: String = "asClosable"
}

Is there any configuration exposed through sbt that would allow us to pass in the flag?