prepareOffline does not install the relevant compiler-bridge?

[yilinwei]

I got bitten by this because I'm constructing a coursier cache using coursier's fetch JSON report on 0.10.12 to run mill in a completely sandboxed environment.

> myapp.compile java.util.NoSuchElementException: None.get
       >     scala.None$.get(Option.scala:627)
       >     scala.None$.get(Option.scala:626)
       >     mill.scalalib.ZincWorkerModule.$anonfun$worker$5(ZincWorkerModule.scala:48)
       >     mill.scalalib.worker.ZincWorkerImpl.compileBridgeIfNeeded(ZincWorkerImpl.scala:216)
       >     mill.scalalib.worker.ZincWorkerImpl.withCompilers(ZincWorkerImpl.scala:389)
       >     mill.scalalib.worker.ZincWorkerImpl.compileMixed0(ZincWorkerImpl.scala:338)
       >     mill.scalalib.worker.ZincWorkerImpl.compileMixed(ZincWorkerImpl.scala:306)
       >     mill.scalalib.ScalaModule.$anonfun$compile$2(ScalaModule.scala:198)
       >     mill.define.Task$TraverseCtx.evaluate(Task.scala:380)

I can see there was some work done on it in this commit. I haven't yet had the time to upgrade to a newer mill version to see if the issue is still there.

[natsukagami]

I got hit by this today with 0.11.4 as well

compile java.lang.Exception: Failed to load compiler bridge for 3.3.1 org.scala-lang
    mill.scalalib.ZincWorkerModule.$anonfun$worker$6(ZincWorkerModule.scala:81)
    scala.Option.getOrElse(Option.scala:201)
    mill.scalalib.ZincWorkerModule.$anonfun$worker$5(ZincWorkerModule.scala:81)
    mill.scalalib.worker.ZincWorkerImpl.compileBridgeIfNeeded(ZincWorkerImpl.scala:255)
    mill.scalalib.worker.ZincWorkerImpl.withCompilers(ZincWorkerImpl.scala:387)
    mill.scalalib.worker.ZincWorkerImpl.compileMixed(ZincWorkerImpl.scala:331)
    mill.scalalib.ScalaModule.$anonfun$compile$2(ScalaModule.scala:212)
    mill.define.Task$TraverseCtx.evaluate(Task.scala:71)
    ```

[lefou]

Currently, you need to set the all flag to resolve the compile bridge

$ mill __.prepareOffline --all

But this makes no sense, as it is always required when compiling, so I will open a PR to fix that.