Compile benchmarks in CI

None of the CI dashboard configurations actually turn on the benchmarks. There should one or more dashboard configurations that compile the benchmarks to ensure that changes do not break the benchmarks.

Turning on compiling benchmarks can be done by adding +benchmark to VTKM_SETTINGS in the yaml configuration file. However, compiling the benchmarks requires the Google benchmark library to be installed on the local system, so that might need to be set up in the docker images.