How to configure javaHome for Scala compilation?

[lihaoyi]

It seems only the Java compiler supports setting javaHome. Could we expose a way to set it for Scala as well?

[eed3si9n]

The base-level assumption both sbt and Zinc has been making is that JIT is expensive for scala-library and scala-compiler, likely based on the observation back then. Stemming from the assumption, currently it tries to avoid shelling out new JVM for Scala compilation, and where possible fakes it by making function calls into a sandboxed ClassLoader.

I think it would be useful to be able to fork out Zinc operation for various purposes, but it would require some thinking to support shelling out different scenarios.