Hack fix to align script body dynscopes with top-level-binding

* Not sure if this is the right fix, but pushing it into the repo
  so that at least interp doesn't break on the following tests:

  jruby -X-C -e "x = 1; eval 'p x', TOPLEVEL_BINDING"

* This fix lets me run bundle install for rails/activesupport.

* Once verified and we have a fix that works for both JIT and interp,
  we need tests for this.