root@8693c627f5de:/concurrent-ruby# jruby -S rake compile:java
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by jnr.posix.JavaLibCHelper$ReflectiveAccess to method sun.nio.ch.SelChImpl.getFD()
WARNING: Please consider reporting this to the maintainers of jnr.posix.JavaLibCHelper$ReflectiveAccess
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
LoadError: no such file to load -- /usr/share/rubygems-integration/all/gems/rake-12.3.1/exe/rake
    load at org/jruby/RubyKernel.java:974
  <main> at /usr/local/bin/rake:23