Add option to jest to run tests only locally, or on linux (#2609)

Summary:
Pull Request resolved: https://github.com/facebook/flipper/pull/2609

Make it possible to mark some tests to run on non-CI, or unix only

Reviewed By: nikoant

Differential Revision: D29813506

fbshipit-source-id: 140f8a4eaed5af3282ab9d139b46a52818be0934

desktop/jest.config.js

@@ -13,6 +13,7 @@ module.exports = {
     '\\.(js|tsx?)$': '<rootDir>/scripts/jest-transform.js',
   },
   setupFiles: ['<rootDir>/scripts/jest-setup.js'],
+  setupFilesAfterEnv: ['<rootDir>/scripts/jest-setup-after.js'],
   moduleNameMapper: {
     '^flipper$': '<rootDir>/app/src',
     '^flipper-plugin$': '<rootDir>/flipper-plugin/src',