Fix incremental compilation when a Scala project depends on a Java project (#414)

* Upgrade ammonite to 1.1.2-30-53edc31

This is mainly to get https://github.com/lihaoyi/Ammonite/pull/851 which
should reduce the amount of unnecessary work done by incremental
compilation in the Mill build. This requires some code changes since
this means we now depend on a more recent version of coursier, as a
side-effect this means that we do not depend on scalaz anymore.

Also use the same ammonite version in the Mill build and in
ScalaModule#ammoniteReplClasspath.

Also remove an incorrect dependency in the caffeine integration test.
This was always wrong but did not start failing until this commit,
probably due to dependencies appearing in a different order on the
classpath.

* Rename ScalaWorker to ZincWorker

Starting with the next commit, it will be used in Java-only projects
too, so the name is misleading.

* Upgrade to Zinc 1.2.1

* Fix incremental compilation when a Scala project depends on a Java project

Before this commit, JavaModule#compile simply called javac
unconditionally, thus generating new classfiles every time. But if a
Scala project depends on a Java project, this will throw off the
incremental compilation algorithm which will unnecessarily recompile
files. To avoid this we now use Zinc to compile Java projects too (as a
bonus this means that Java compilation becomes incremental). This
required some refactoring in ZincWorkerImpl to be able to compile stuff
without having to pass Scala-specific options.

The issue solved by this commit could be reproduced by running in the
Mill repository:

$ mill main.compile
$ mill -i
@ main.compile()

and observing that before this commit, the `main.compile()` call ended
up recompiling code.

1 files changed, 2 insertions, 2 deletions

diff --git a/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala b/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
index 5e4fc471..748afb79 100644
--- a/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
+++ b/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
@@ -46,7 +46,7 @@ trait ScalaNativeModule extends ScalaModule { outer =>
   override def artifactSuffix: T[String] = s"${platformSuffix()}_${artifactScalaVersion()}"
 
   trait Tests extends TestScalaNativeModule {
-    override def scalaWorker = outer.scalaWorker
+    override def zincWorker = outer.zincWorker
     override def scalaOrganization = outer.scalaOrganization()
     override def scalaVersion = outer.scalaVersion()
     override def scalaNativeVersion = outer.scalaNativeVersion()
@@ -238,7 +238,7 @@ trait TestScalaNativeModule extends ScalaNativeModule with TestModule { testOute
   // creates a specific binary used for running tests - has a different (generated) main class
   // which knows the names of all the tests and references to invoke them
   object testRunnerNative extends ScalaNativeModule {
-    override def scalaWorker = testOuter.scalaWorker
+    override def zincWorker = testOuter.zincWorker
     override def scalaOrganization = testOuter.scalaOrganization()
     override def scalaVersion = testOuter.scalaVersion()
     override def scalaNativeVersion = testOuter.scalaNativeVersion()