CI: JRuby builds fail

[olleolleolle]

This Issue is about the CI build failures on JRuby.

Issues noted

• the jruby-19mode installs JRuby 9.2.5.0, which represents... what, really? (Found remote file https://repo1.maven.org/maven2/org/jruby/jruby-dist/9.2.5.0/jruby-dist-9.2.5.0-bin.tar.gz). The last 1.9 would be jruby-1.7.27, but his is long out of support.
• Fails on installing byebug C extension
• JRuby 9.2.12.0 has fixed all the Illegal Access module issues, according to its latest blog post about that release.

[HarlemSquirrel]

Thanks for reporting! These are all fixed now with #363 and #365

[olleolleolle]

That's awesome! Thanks a lot for taking care of this.