Remove fs and os usage from Mobile Builds plugin

Summary: Changelog: Expose env info and FS rm command to flipper plugins.

Reviewed By: mweststrate

Differential Revision: D32988478

fbshipit-source-id: 3d0233f9eb34d3478b07e39b9401c0e30ca95135

desktop/flipper-common/src/index.tsx

@@ -21,6 +21,7 @@ export {sleep} from './utils/sleep';
 export {timeout} from './utils/timeout';
 export {isTest} from './utils/isTest';
 export {assertNever} from './utils/assertNever';
+export {fsConstants} from './utils/fsConstants';
 export {
   logPlatformSuccessRate,
   reportPlatformFailures,