Make sbt-stainless work without requiring an external solver

[dotta]

Currently, sbt-stainless expects an external solver to be installed and available in the $PATH. This because I couldn't make scalaz3 work on OSX (see epfl-lara/ScalaZ3#56).

Once the scalaz3 ticket is resolved, we should publish a stainless-scalac-plugin embedding scalaz3 for each supported os and architecture. This way, sbt-stainless will be usable without having to install an external solver.

I've started working on this ticket in this branch: https://github.com/dotta/stainless/tree/wip/include-scalaz3-in-fat-jar

[vkuncak]

@romac is this still an issue?

[romac]

Not in the sense that we support Princess out of the box, and having z3 support just requires installing Z3. But yeah, we do not currently ship NativeZ3 with the compiler plugin, which we perhaps should?