ExecuteMojo doesn't update Ruby classloader to plugin classloader

[byteit101]

When using pom.rb, the Parser uses the coreExtension>io.takari.polyglot:polyglot-ruby classloader. When executing the mojos, the Thread context classloader is the plugin>io.takari.polyglot:polyglot-maven-plugin classloader with custom dependencies added, but JRuby still uses the "coreExtension" classloader.

Ruby execute blocks should pick up dependencies added:

# ...
plugin!('io.takari.polyglot:polyglot-maven-plugin', VERSIONS[:polyglot_version]) do
    dependency( 'org.apache.maven.shared', 'maven-dependency-tree', '3.2.1')
end

execute :install_gems, :'initialize' do |ctx|
    org.apache.maven.shared.dependency.graph.DependencyGraphBuilder # => Exception!
end
# ...