docs: public String getKernelDefinition(BootstrapConfig bootProps) {
          String kernelDef = bootProps.get(BOOTPROP_KERNEL);
  
          if (kernelDef == null)
              kernelDef = defaults.getProperty(MANIFEST_KERNEL);
  
          if (kernelDef != null)
              bootProps.put(BOOTPROP_KERNEL, kernelDef);
  
          return kernelDef;
      }