We discussed with engflow the problem with the number of invocations we are generating. Currently in a scons build, we will batch targets up and perform multiple invocations of bazel during a single scons build. This was done to support a developer use case were you may be building specific targets and we wanted bazel to only build what was actually needed.

However, the vast majority of developer use cases are with ninja, which by default does up front bazel builds. The majority of uses of pure scons builds is in the CI, where we generally are not building specific targets, and usually build meta targets like install-devcore or install-all. With these larger targets, bazel will generally be asked to build every anyways, so in that case it makes sense to do up front bazel builds.

We should add a scons command line option "BAZEL_BUILD_UPFRONT" that will primarily be used in CI, that will perform an upfront build everything bazel build ("bazel build //...") in a thread before scons starts building targets (SCons would still walk and look for targets to build).