This pulls down the prebuilt ceres libraries and uses them with Bazel to
build and test wpical.
Do note that bazel looks up artifacts used for testing differently than
the other build systems. It wants you to use its runfiles API to find
the dependencies reliably. Add a function to look up the paths for
files, and use runfiles only when building with Bazel to maintain
compatibility with other languages.
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
