Polyglot extensions not loading in all circumstances

[headius]

Currently ruby-maven is set up to copy its .mvn/extensions.xml file into the current directory when running poms from the Ruby API. This is intended to load the ruby polyglot extension, so it is always enabled and nothing more is required for ruby-maven users to user this dialect. Unfortunately due to issues discussed in jruby/jruby#7059 (comment), the current directory is not always used by Maven when looking for extensions for the current build.

We should use something more robust to ensure that Maven as run through ruby-maven always has polyglot enabled, without playing config file tricks.

[headius]

@mkristian I could use some help here! Not sure how to get ruby-maven-libs to build with the ruby polyglot extension shipped in-the-box.

[headius]

Things are moving forward here: takari/polyglot-maven#319

Based on @cstamas recommendation, we will be moving forward with integrating polyglot directly into the Maven distribution packaged in ruby-maven. This will allow polyglot to be "always on" and not depend on the location of .mvn/extensions.xml.

It turns out there were some tweaks needed in polyglot to build a custom polyglot maven in this way, which are contained in the above PR.

We will be standing by to support the updated polyglot release, and then need to integrate it back into ruby-maven for our own release. That will provide the ultimate fix for the jar-dependencies issue (jruby/jruby#7059) without needing to modify jar-dependencies.

[headius]

This was partially fixed by ruby-maven-libs update to 3.9.9, which allowed extensions to be activated at a filesystem root again (https://issues.apache.org/jira/browse/MNG-8165).

The remaining fix is in #11 and ships the extension as part of the Maven distribution so it is always active for ruby-maven.