fix: install libc++-dev during benchmarks workflow run

[Envoy-VC]

Description

Fixes issue where .github/workflows/benchmarks.yml fails to run.

Problem

Resolves #17

Summary

Added libc++-dev install command in the Install bb Step

sudo apt install libc++-dev

Updated Compare gates reports step to use latest commit

uses: noir-lang/noir-gates-diff@dbe920a8dcc3370af4be4f702ca9cef29317bec1

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[TomAFrench]

Thank you for flagging this issue up @Envoy-VC. I've pulled these changes into #19 where CI is passing so we're probably going to merge that PR instead.