If the builds are slow, build accelerators can help a lot. Ccache would work for sure and there is also firebuild, that can accelerate the linker phase and many other tools in builds.
If you would like to make similar hooks work again on macOS, check out this guide: https://firebuild.com/setup-macos .
Firebuild uses similar technique to explore the process tree and create a report with CPU utilizations highlighted in a graphical process tree graph.
I was in a similar situation and I laid down the cards.
I think I did the right thing by doing so and the client will reevaluate the viability of the concept as they said.