This largely reproduces the upstream one, but has a few advantages:
1) It initializes LLVM which can be important if we use the backends.
2) It parses commandline flags with Abseil allowing the use of Abseil
flags in benchmarks.
3) It flips the default for tabular display of results which we use
pretty heavily.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
