Function resolve_kernel_dir 

pub fn resolve_kernel_dir(
    path: &Path,
    cli_label: &str,
    cpu_cap: Option<CpuCap>,
) -> Result<PathBuf>

Resolve a kernel directory: auto-build from source tree.

Requires Makefile + Kconfig. Checks cache for clean trees, delegates to kernel_build_pipeline on miss. cli_label prefixes status output and is passed through to kernel_build_pipeline as the diagnostic label.

cpu_cap forwards the resource-budget cap to the pipeline. None is the default for non-kernel-build callers (test/coverage/shell auto-build paths) — --cpu-cap lives on the explicit kernel-build entrypoint, not test-running commands, because the auto-build-on-miss path already runs inside a test invocation where perf-mode constraints dominate.