A bazel build and regression harness for s2geometry

[spendres]

See issue #53.

This version relies on the bazel central repository for abseil-cpp, googletest, and boringssl and points to HEAD of s2geometry.

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[spendres]

...logging.h was removed in most recent commit/push.

[spendres]

I tested build times for a hierarchical library definition as compared to a single flat library definition for s2. The flat definition builds twice as fast (12 sec vs 25 sec) about 25% of the time – using a mac M1. This is counter to expectations, so I reverted to the flat definition.

[spendres]

Thanks for the requested changes by mmorel-35 … made and pushed.

[jmr]

Thank you!