feat(scripts): Support multiple bundles in react-native-xcode.sh

[fivecar]

Summary:

This enables projects to have multiple bundles built during the Xcode bundling phase (e.g. for projects where you might have a PhoneScene and a CarPlayScene each with their own RootView and bundle, if you're using react-native-carplay).

Changelog:

[IOS] [ADDED] - User-configurable BUNDLE_NAME when building bundles

Test Plan:

Built my project with the following Xcode "Bundle React Native code" build step:

set -e

export SOURCEMAP_FILE="$(pwd)/../main.jsbundle.map";
SOURCEMAP_FILE="$(pwd)/../main.jsbundle.map"

WITH_ENVIRONMENT="../node_modules/react-native/scripts/xcode/with-environment.sh"
REACT_NATIVE_XCODE="../node_modules/react-native/scripts/react-native-xcode.sh"

/bin/sh -c "BUNDLE_NAME=main $WITH_ENVIRONMENT $REACT_NATIVE_XCODE"
/bin/sh -c "BUNDLE_NAME=carplay $WITH_ENVIRONMENT $REACT_NATIVE_XCODE"

Then launched the app with a modified AppDelegate.swift which loaded main.jsbundle into one RootView and carplay.bundle into another RootView.

[blakef]

cc @cipolleschi thoughts?

[cipolleschi]

Thanks @fivecar to work on this.
I left a small suggestion to improve the code readability and maintainability.

[fivecar]

Thanks, @cipolleschi! I was the FB LON site lead for its first few years; it's gratifying to have this approved by you. 😄

It looks from the PR that the rest of the workflow needs to be done by maintainers. Please LMK if there's anything else I should be doing on this.

[facebook-github-bot]

@cipolleschi has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@cipolleschi merged this pull request in f8287e2.

[react-native-bot]

This pull request was successfully merged by @fivecar in f8287e2

^{When will my fix make it into a release? | How to file a pick request?}