yet-to-be-merged libregex is not testing dynamic regexps

I previously relied on an abuse of bootstrapping to test dynamic regexps during stage1 and native regexps during stage2, but it turns out stage1 tests aren't run by the bots. Since dynamic and native regexps use different code, it's imperative that both are tested.

I have a fix coming soon that will push dynamic and native regexp testing into stage2.
