Summary:
`gkx` module was added to the codebase and it doesn't exist outside www.
adding all necessary mocks to fix the build
Pull Request resolved: https://github.com/facebookexperimental/Recoil/pull/332
Reviewed By: drarmstr
Differential Revision: D22062299
Pulled By: aaronabramov
fbshipit-source-id: e61dbca322321e4a79d01b3c6d5ae954053c2bfb
