Input needed: Plan for packaging scala

[Katherine Cox-Buday <cox.katherine.e@gmail.com>]

Hi all,

I'm planning to have a go at packaging scala. This is my first time
packaging software of any kind, let alone for Guix, so guidance is
appreciated!

I'm brand-new to scala, but it appears that building it from source
involves circular dependencies. Here's the situation:

- scala 2.12.1 is the latest version. To build it from source, a tool
  called "sbt" (scala build tool) is required.
- sbt 0.13 is the latest version. To build it from source requires a
  prior version of sbt.
- I was able to find older versions[1] of sbt which can be built with
  only scala.
- scala 2.9.2 appears to be the last version that can be built with ant.

So, to untangle this knot to achieve reproducibility, I was planning on
first packaging scala 2.9.2, then the latest version of sbt that could
be built with scala, then sbt 0.13 (which would be useful in its own
right as a package), and then finally scala 2.12.1.

The build for scala 2.9.2 attempts to pull some libraries from a remote
source, so I'm assuming I'll need to also package those?

For a new contributor, this is a pile of work, but I don't mind too much
since my need drives me, and I'll be learning more about Guix in the
process :) I do, however, want to confirm that this is a sane plan
before I set out on this journey. It would be easier if I could just do
a binary package to bootstrap the toolchain and back-fill when I have
more experience, but I wasn't sure if that is acceptable.

[1] - https://github.com/sbt/sbt-zero-seven

-- 
Katherine