Scala Native unit tests do not work with JVM 21 about scala-native HOT 2 CLOSED

Analysis.

I have read that Scala 2.12.17 and below do not support Java 21. Scala 2.12.18 is the first version which does.
As one of the steps towards Scala Native supporting Java 21, it needs to use a version of sbt which itself
uses Scala 2.12.18 (or one which supports Java 21).

Sbt 1.9.0 is the first version of sbt which uses Scala 2.12.18. Sbt 1.9.4 fixes a CVE (Common Vulnerabilities and Exposures).
Sbt 1.9.6 is the current version and is used in project/build.properties.

As long as we are picking an sbt 1.9.n version, it seem rational to use the version which is both current
and specified in project/build.properties. Eventually, the two will grow out of synch together.

./scripted-tests/run/backtrace/project/build.properties and
./scripted-tests/scala3/cross-version-compat/project/build.properties
both specified version of sbt which do not support Java 21. I left them in place with
a comment describing the commenting out of an explicit sbt version and the new inheritance
from the project/ScalaVersions.scala specification (note well: not the project/build.properties)

from scala-native.

Reference: sbt 1.6.2 & Java 21

from scala-native.