If using cmake, you can try a unity build. https://cmake.org/cmake/help/latest/prop_tgt/UNITY_BUILD.htm...

You can also specify a `-DUNITY_BUILD_BATCH_SIZE` to control how many get grouped, so you can still get some parallelism. However, I think it'd be more natural to be able to specify number of batches (e.g. `nproc`) than their size.

Code bases may need some updating to work.