docJar fails to generate links to standard library

[TheElectronWill]

The problem

Links to standard Java and Scala classes aren't generated properly by docJar, resulting in a ScalaDoc that contains plain text instead of a proper link. Linking to a class in the project does work.

Should I add some docJar options to fix this? I feel like this should work out-of-the box, if possible.

Reproducible example

build.sc

import mill._, scalalib._

object foo extends ScalaModule {
  def scalaVersion = "2.12.6"
}

foo/src/foo/bar/Test.scala

package foo.bar

import java.nio.ByteBuffer

/** ==ScalaDoc test==
  *  - Link to the standard Scala library: [[scala.collection.Seq]]
  *  - Link to the standard Java library: [[java.util.List]]
  *  - Link to an imported class: [[ByteBuffer]]
  */
class Test {}

Output:

model contains 4 documentable templates
foo/src/foo/bar/Test.scala:5: warning: Could not find any member to link for "scala.collection.Seq".
/** ==ScalaDoc test==
^
foo/src/foo/bar/Test.scala:5: warning: Could not find any member to link for "java.util.List".
/** ==ScalaDoc test==
^
foo/src/foo/bar/Test.scala:5: warning: Could not find any member to link for "ByteBuffer".
/** ==ScalaDoc test==
^

[Sailsman63]

I know this is an old question. If it's still of interest, note that vanilla command-line javadoc doesn't do this either unless you explicitly -link it.