Launching ammonite causes scala.reflect.internal.MissingRequirementError on Java != 8

Not sure if this belongs here or in ammonite or maybe even nixpkgs, but let me try:

I have the problem, that I can only launch ammonite via coursier with Java 8. 11 and 14 result in this error:

```
$ coursier launch com.lihaoyi:ammonite_2.13.3:2.3.8 -M ammonite.Main
Loading...
Welcome to the Ammonite Repl 2.3.8 (Scala 2.13.3 Java 14.0.2-internal)
@ // press RETURN or any expression whatsoever
scala.reflect.internal.MissingRequirementError: object java.lang.Object in compiler mirror not found.
scala.reflect.internal.MissingRequirementError$.notFound(MissingRequirementError.scala:24)
scala.reflect.internal.Mirrors$RootsBase.$anonfun$getModuleOrClass$6(Mirrors.scala:66)
scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:66)
scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:56)
scala.reflect.internal.Mirrors$RootsBase.getRequiredClass(Mirrors.scala:56)
scala.reflect.internal.Definitions$DefinitionsClass.ObjectClass$lzycompute(Definitions.scala:287)
scala.reflect.internal.Definitions$DefinitionsClass.ObjectClass(Definitions.scala:287)
scala.reflect.internal.Definitions$DefinitionsClass.init(Definitions.scala:1608)
scala.tools.nsc.Global$Run.(Global.scala:1214)
ammonite.interp.Compiler$$anon$1.(Compiler.scala:274)
ammonite.interp.Compiler$.apply(Compiler.scala:142)
ammonite.interp.CompilerLifecycleManager.init(CompilerLifecycleManager.scala:89)
ammonite.interp.CompilerLifecycleManager.preprocess(CompilerLifecycleManager.scala:57)
ammonite.interp.Interpreter.$anonfun$processLine$4(Interpreter.scala:251)
ammonite.util.Res$Success.flatMap(Res.scala:62)
ammonite.interp.Interpreter.$anonfun$processLine$2(Interpreter.scala:244)
ammonite.util.Catching.flatMap(Res.scala:115)
ammonite.interp.Interpreter.processLine(Interpreter.scala:243)
ammonite.repl.Repl.$anonfun$action$8(Repl.scala:197)
ammonite.util.Res$Success.flatMap(Res.scala:62)
ammonite.repl.Repl.$anonfun$action$4(Repl.scala:184)
ammonite.repl.Scoped.$anonfun$flatMap$1(Signaller.scala:45)
ammonite.repl.Signaller.apply(Signaller.scala:28)
ammonite.repl.Scoped.flatMap(Signaller.scala:45)
ammonite.repl.Scoped.flatMap$(Signaller.scala:45)
ammonite.repl.Signaller.flatMap(Signaller.scala:16)
ammonite.repl.Repl.$anonfun$action$2(Repl.scala:176)
ammonite.util.Catching.flatMap(Res.scala:115)
ammonite.repl.Repl.action(Repl.scala:168)
ammonite.repl.Repl.loop$1(Repl.scala:208)
ammonite.repl.Repl.run(Repl.scala:223)
ammonite.Main.$anonfun$run$1(Main.scala:223)
scala.Option.getOrElse(Option.scala:201)
ammonite.Main.run(Main.scala:211)
ammonite.MainRunner.$anonfun$runRepl$1(Main.scala:415)
ammonite.MainRunner.watchLoop(Main.scala:396)
ammonite.MainRunner.runRepl(Main.scala:415)
ammonite.Main$.main0(Main.scala:321)
ammonite.Main$.main(Main.scala:270)
ammonite.Main.main(Main.scala)
jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:564)
coursier.cli.launch.Launch$.$anonfun$launch$6(Launch.scala:180)
coursier.cli.launch.Launch$.$anonfun$launchCall$13(Launch.scala:354)
coursier.cli.launch.Launch$.run(Launch.scala:540)
coursier.cli.Coursier$.$anonfun$runA$2(Coursier.scala:157)
coursier.cli.Coursier$.$anonfun$runA$2$adapted(Coursier.scala:139)
coursier.cli.CommandAppPreA.run(CommandAppPreA.scala:22)
caseapp.core.app.CommandAppWithPreCommand.$anonfun$main$5(CommandAppWithPreCommand.scala:99)
caseapp.core.app.CommandAppWithPreCommand.$anonfun$main$5$adapted(CommandAppWithPreCommand.scala:99)
scala.util.Either.fold(Either.scala:191)
caseapp.core.app.CommandAppWithPreCommand.$anonfun$main$3(CommandAppWithPreCommand.scala:99)
caseapp.core.app.CommandAppWithPreCommand.$anonfun$main$3$adapted(CommandAppWithPreCommand.scala:85)
scala.Option.foreach(Option.scala:407)
caseapp.core.app.CommandAppWithPreCommand.main(CommandAppWithPreCommand.scala:85)
coursier.cli.Coursier$.main(Coursier.scala:104)
coursier.cli.Coursier.main(Coursier.scala)
jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
java.lang.reflect.Method.invoke(Method.java:564)
coursier.bootstrap.launcher.a.a(Unknown Source)
coursier.bootstrap.launcher.Launcher.main(Unknown Source)

```
This probably has something to do with the fact that I am on NixOS, but the issue is also reproducible via this docker image

```
FROM nixos/nix

RUN nix-channel --add https://nixos.org/channels/nixpkgs-unstable nixpkgs
RUN nix-channel --update

RUN nix-env -iA nixpkgs.ncurses
RUN nix-env -iA nixpkgs.coursier
```

with

```
docker build . -t repro
docker run -it repro coursier launch com.lihaoyi:ammonite_2.13.3:2.3.8 -M ammonite.Main
```

As ammonite works as expected with other Java versions when running outside of coursier, I think it must be some interaction between coursier, ammonite and the way nix works or how [coursier is packaged in nixpkgs](https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/coursier/default.nix) (which looks inconspicuous as far as I can tell, though). Running e.g. scalafmt via `coursier launch` in the above manner does not exhibit the same behaviour.

Unfortunately I apparently am not competent enough to get to the bottom of this myself. Has anyone else seen this happen? I initially stumbled upon this because `bloop console ` (which in turn calls roughly the above command + adding the project classpath) has the same problem.