Summary:
I relied too much on the types which in this case don't help at all.
Filtering on a promise will just automatically get all values to pass.
Pull Request resolved: https://github.com/facebook/flipper/pull/3008
Test Plan: `yarn build --mac` works again on the GH checkout.
Reviewed By: mweststrate
Differential Revision: D31991576
Pulled By: passy
fbshipit-source-id: f632d29ddfc09b7130b68b4b17264fd30e1969ce