Create scripts for building patched React Native

[hsource]

Motivation

As part of Task 1.1: Build React Native 0.81 in an empty test project, we need to make sure we can build a fork of React Native that builds with a test project.

This PR creates scripts that can be used with the instructions there to build a fork of React Native.

Changes

Before starting, I did these steps: How did we figure out the steps for “Create scripts for building patched React Native”

Build scripts

• Add scripts/build-package.js to build iOS artifacts
  • Downloads and expands Hermes source if missing
  • Copies Hermes engine files to the Hermes source folder
  • Builds types and FBReactNativeSpec
  • Builds Hermes and hermesc binaries for macOS
  • Copies built binaries to sdks/hermesc/osx-bin
• Add scripts/move-react-native-package.sh to move react-native package files to root
  • Moves all root files to a saved-root-files directory
  • Moves contents of packages/react-native to root
  • Updates .gitignore to remove /packages/react-native/ from paths and allow required files
  • Supports --reverse flag to undo the move

Gradle configuration

• Add publishAllToGitLab task in build.gradle.kts to publish Android artifacts to GitLab Maven repository
• Add GitLab Maven repository configuration in packages/react-native/ReactAndroid/publish.gradle
  • Configures authentication using gitlabPrivateToken property
  • Points to GitLab project packages endpoint

Testing

1. Follow instructions in Part 3b: upload Android JARs and create tag to install to run the scripts
2. Install the package using yarn add wanderlog/react-native#v0.81.5-wanderlog.11
3. Clean the build pushd android && ./gradlew clean && popd && cd ios && xcodebuild clean -workspace wanderlog.xcworkspace -scheme wanderlog`
4. Run yarn android and yarn ios and verify they work

[julesyoungberg]

LGTM. One comment about potentially adding a dry-run option to the script for moving files.

Docs also look good. Might be a typo at the start of Part 3b under 'Why we need to do this': 'When building the an Android the app directly builds them using the React Native JARs.'

Also, would it be worth creating a script out of the codeblock at the end of Part 3b?