We've been running Octane/regexp all wrong in run-jsc-benchmarks

We've been running Octane/regexp all wrong in run-jsc-benchmarks
https://bugs.webkit.org/show_bug.cgi?id=154827

Reviewed by Andreas Kling.

Octane v.2 and JetStream v.1.1 run this benchmark with warmup. This script was running
it without warmup. This patches fixes this by making this script run it with warmup.

This fix shows that my last patch, which added FTL support for regexp, was actually a 3%
speed-up on Octane/regexp, not a slow-down as the ChangeLog claimed.

It discovered this bug because for each Octane test that I want to debug, I usually make
a standalone .js file that contains the whole test along with a miniharness - usually
a plain loop - that runs it almost like it would for real but with whatever hacks I'm
using for debugging. When I wrote such a thing for regexp, I used a ~20 iteration warmup
to match the one second of warmup that this benchmark gets in Octane. To my surprise,
this quite faithful regexp runner did not see the regression that run-jsc-benchmarks
saw. That's when I found out that run-jsc-benchmarks was running it wrong.

The reason for the no-warmup slow-down is that the FTL is actually fairly expensive to
run on some of these very large functions in the regexp benchmark. I don't think we can
do anything about that, and I'd argue that the speed-up we see after the compilation is
done suggests that it was worth it.

* Scripts/run-jsc-benchmarks:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@197361 268f45cc-cd09-0410-ab3c-d52691b4dbfc