try to fix classloading issues on runLocal and test with java 9 (#255)

* fix class loading for inprocess in java 9

* always add rt jar in case of java 9

* move all custom classloading logic into mill.util.ClassLoader

* add comments explaining parent class loader changes and comment in tests pointing to original issue

1 files changed, 3 insertions, 0 deletions

diff --git a/build.sc b/build.sc
index bc3c3cf3..a0e563c3 100755
--- a/build.sc
+++ b/build.sc
@@ -25,6 +25,9 @@ trait MillPublishModule extends PublishModule{
       Developer("lihaoyi", "Li Haoyi","https://github.com/lihaoyi")
     )
   )
+
+  def javacOptions = Seq("-source", "1.8", "-target", "1.8")
+
 }
 object moduledefs extends MillPublishModule{
   def ivyDeps = Agg(