Function make_kernel_with_output 

pub fn make_kernel_with_output(
    kernel_dir: &Path,
    progress: Option<&FetchProgress>,
    jobs_override: Option<usize>,
) -> Result<()>

Build the kernel with output piped through the progress group.

jobs_override supplies the -jN count when set (used by kernel_build_pipeline under --cpu-cap to keep gcc’s parallelism aligned with the reserved CPU count). None falls back to std::thread::available_parallelism.