When I launch a single-file source-code program that uses incubator modules, I get duplicate warnings:

  $ echo 'public class Foo { public static void main(String ... args) { } }' >Foo.java
  $ java --add-modules jdk.incubator.vector Foo.java
  WARNING: Using incubator modules: jdk.incubator.vector
  warning: using incubating module(s): jdk.incubator.vector
  1 warning
  $

We should omit the second warning, which is issued by the compiler. This could be done in the compiler via a special -XD option, or by checking which file manager is in use since the source launcher has a custom file manager.