Support GraalVM native image on Scala 3

To build a cats-effect 3 app with Scala 3 and GraalVM native image, one currently has to set some configuration options, otherwise the build falls back to a version that requires a JDK.

This is what the native-image agent generated for me:

[
{
  "name":"cats.effect.unsafe.IORuntimeCompanionPlatform",
  "fields":[{"name":"0bitmap$1", "allowUnsafeAccess":true}]
},
{
  "name":"cats.effect.unsafe.WorkStealingThreadPool",
  "fields":[{"name":"0bitmap$1", "allowUnsafeAccess":true}]
},
{
  "name":"java.lang.invoke.VarHandle"
},
{
  "name":"sun.misc.Unsafe",
  "allDeclaredFields":true
}
]

(passed with -H:ReflectionConfigurationFiles)

Maybe we can include some version of this in the jar itself, so users don’t need to bother with these options: https://www.graalvm.org/reference-manual/native-image/BuildConfiguration/

Here’s a sample app built with this config: https://github.com/kubukoz/graalvm-native-ce3/ (note that the options aren’t necessary when building with Scala 2.13.6)

[kubukoz]

Maybe some of this could be attached to the dotty runtime? 😄

[djspiewak]

Agreed. I think this works fine.