Regression from PR #47458: Cannot install React Native from Git anymore

Description

This PR updates shouldSkipGenerationForRncore as such it checks if .../ReactCommon exists before deciding to skip rncore generation, whereas previously it would check .../ReactCommon/react/renderer/components/rncore specifically.

This change breaks installations from Git.

I noticed this while upgrading from 0.76.2 to 0.78.1.

Per my debugging:

• Previous behavior:
  • When installing from NPM: rncore is pre-generated using the prepack script
  • When installing from Git: rncore gets generated when running pod install
• Current behavior:
  • When installing from NPM: rncore is pre-generated using the prepack script
  • When installing from Git: rncore will NOT get generated when running pod install because .../ReactCommon is detected as exists even though .../ReactCommon/react/renderer/components/rncore does not

Steps to reproduce

npx @react-native-community/cli@latest init BuggyReactNative
cd ./BuggyReactNative/
npm install 'https://gitpkg.vercel.app/facebook/react-native/packages/react-native?0.78-stable'
cd ./ios/
bundle exec pod install
cd ..
ls ./node_modules/react-native/ReactCommon/react/renderer/components/rncore
# 💥 no such file or directory
# 💥 Xcode won't build the project

React Native Version

0.78.1

Affected Platforms

Runtime - iOS, Other (please specify)

Output of npx @react-native-community/cli info

Not relevant

Stacktrace or Logs

Not relevant

Reproducer

Run the reproducer bash script so you can test with your toolchain not mine

Screenshots and Videos

No response

Start in packages/react-native/scripts/codegen/generate-artifacts-executor.js at shouldSkipGenerationForRncore and compare the referenced earlier behavior with the current ReactCommon check. Use the issue's Git installation reproducer and bundle exec pod install to verify the generation path. Done means the rncore directory exists after installation and the iOS project can build.