'Called before ruby modules\' install() methods.  Sets GEM_HOME
and GEM_PATH to values appropriate for the package being built.
In most cases, extensions will only need to have one line::
gem(\'install\', \'<gem-name>.gem\')'

def setup_dependent_package(self, module, dependent_spec):

    module.ruby = Executable(join_path(self.spec.prefix.bin, 'ruby'))
    module.gem = Executable(join_path(self.spec.prefix.bin, 'gem'))
