Hi @Nathan_Delhaye,
It seems there is issue with jruby native code libjffi.so . gradle downloads jruby under vendor/ and uses that to execute rake artifact:rpm. Try downloading jruby by
gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB && \
\curl -sSL https://get.rvm.io | bash -s stable --ruby=jruby-9.1.13.0
Then set path to your jruby installation.
Also you would need bundler which can be installed by jruby -S gem install bundler. Then you may invoke jruby -S rake artifact:rpm. But before this you may also need to export USE_RUBY=1 to use your local ruby installation.