"sbt dotr" does not automatically put scala-library on the classpath anymore

[smarter]

This was recently broken (I guess by #3436):

> dotc tests/pos/HelloWorld.scala
> dotr HelloWorld
Exception in thread "main" java.lang.NoClassDefFoundError: scala/Predef$
        at HelloWorld$.main(HelloWorld.scala:2)
        at HelloWorld.main(HelloWorld.scala)
Caused by: java.lang.ClassNotFoundException: scala.Predef$
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 2 more

Workaround: doing dotr -classpath /path/to/scala-library-2.12.4.jar or using the ./bin/dotr script.

[gosubpl]

Works now like a charm. Thanks @nicolasstucki !