Disable iOS build steps (#1019)
Disable iOS build steps (#1019)

Summary:
These haven't built in ages now and causing all sorts of
down-stream issues with Greenkeeper and release jobs. We need to find
a more sustainable way of running them.
Pull Request resolved: https://github.com/facebook/flipper/pull/1019

Test Plan: eyes

Reviewed By: priteshrnandgaonkar

Differential Revision: D21066022

Pulled By: passy

fbshipit-source-id: 0480b7f17ed04af490113cf5dfbbfec130ec9eb3

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