This change makes it so only kernels of the same vendor are compiled in
parallel. For example for the release builds it will be:
1. All CUDA kernels
2. All OptiX kernels
3. All HIP kernels
4. All OneAPI kernels
This potentially leads to a lower CPU utilization, but it makes it much
easier to manage memory usage and tweak per-vendor concurrency.
The goal of this change is to solve occasional out-of-memory during the
GPU kernels compilation step on the CI/CD farm.
This change also includes tweaks to the prallel jobs for HIP-RT and
oneAPI. The tweak is based on measuring apparent memory usage peak on
Linux when doing single-thread compilation, and giving some safe margin
from the available memory on the buildbot.
Pull Request: https://projects.blender.org/blender/blender/pulls/129945
f58522fc10