The compile_all Evergreen task was introduced to split out compiling C++ unit tests into their own Evergreen task to avoid waiting for them to finish prior to running JavaScript tests. It serves as a backstop to ensure every known target can successfully be built by the auto-install subsystem. Now that we are using Bazel and have an build engine which can be queried more rapidly and can answer "are there some targets which are not built from install-dist-test, install-unittests, etc.?", we should look into whether there is still a need for this backstop.