Decouple the building of benchmarks and tests (#2439)

[kgpai]

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Summary: Tests and benchmarks targets are now de-coupled. That means they can be built independently. Shared functionality is moved to a common utility library.

Resolves https://github.com/facebookincubator/velox/issues/1704

X-link: https://github.com/facebookincubator/velox/pull/2439

Reviewed By: Yuhta

Differential Revision: D39484543

Pulled By: kgpai

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D39484543