Exclude directory/file for eslint

The sage 9 based theme should use a library that has been built from source and copied to assets/lib folder. - On build the files should be copied to dist/.
However, eslint complains about linting errors in the library files.
How can I exclude the library folder so eslint never lints it during build?

I solved it by adding a new exclude property to rules object for use: 'eslint',:
exclude: [/(lib\/somelib)/],