Summary:
Runs the `./ios-install-third-party.sh` script as part of the build process to avoid having to do it manually when building the cxx bridge with xcode. Also added the third-party dir to gitignore.
**Test plan**
Tested that just building works when the third-party dir is missing.
Closes https://github.com/facebook/react-native/pull/12694
Differential Revision: D4658165
Pulled By: ericvicenti
fbshipit-source-id: 9b51b88eb26637b19266bf85deafa41e3a77a645
Summary: I broke Circle CI builds by moving a file, so I am updating the OSS build setup with details of the move. Whilst I was testing the change, I noticed that the UI Explorer build was also already broken, so this diff also changes some of its configuration to make it build again.
Reviewed By: javache
Differential Revision: D4579137
fbshipit-source-id: 4cbb1ef148075280b991cbc5bb47bf96ec3d543a
Marc Horowitz
Janic Duplessis
Pieter De Baets
Valentin Shergin
Ashok Menon