Add the ability to use system installed versions of abseil and googletest If the user has checked out the submodules in third_party, they will be used, otherwise we will try and find the system installed versions of these dependencies and use them if they are modern enough. Change-Id: I52164bc48a6ea804b85cdda05fee9cb94632f6c0
Ceres Solver is an open source C++ library for modeling and solving large, complicated optimization problems. It is a feature rich, mature and performant library which has been used in production at Google since 2010. Ceres Solver can solve two kinds of problems.
Please see ceres-solver.org for more information.