bug#45555: [wishlist] Packaging GWT

[Ricardo Wurmus <rekado@elephly.net>]

GWT (http://www.gwtproject.org/) is a toolkit for generating JavaScript
applications from Java.  RStudio is implemented with GWT, so we should
package it if we ever want to offer an RStudio package for Guix.

The GWT repository is here: https://github.com/gwtproject/gwt

This looks easy to build with ant-build-system, but only because all the
bundled dependencies are in a separate repository:

   https://github.com/gwtproject/tools

The “lib” directory contains a large number of Jars that are expected to
be available when building GWT.  It is not clear if all of these
libraries are needed to compile GWT.  Let’s not think about this now and
just package as many of them as possible, leaving the difficult ones for
later.

The bad news is that there are 352 jars.  The good news is that we
already have a few of these packages and that there are a few duplicates
providing different versions of the same tools.

One of the dependencies is the Google Closure Compiler (for
com.google.javascript.jscomp); progress on packaging it is tracked in
issue #45554.

-- 
Ricardo