code: def _create_context_jar(self, compile_context):
      
      root = compile_context.classes_dir.path
      with compile_context.open_jar(mode='w') as jar:
        for abs_sub_dir, dirnames, filenames in safe_walk(root):
          for name in dirnames + filenames:
            abs_filename = os.path.join(abs_sub_dir, name)
            arcname = fast_relpath(abs_filename, root)
            jar.write(abs_filename, arcname)
docs: Jar up the compile_context to its output jar location.
  
      TODO(stuhood): In the medium term, we hope to add compiler support for this step, which would
      allow the jars to be used as compile _inputs_ as well. Currently using jar'd compile outputs as
      compile inputs would make the compiler's analysis useless.
        see https://github.com/twitter-forks/sbt/tree/stuhood/output-jars