Allow apple to configure Hermes as option

[blakef]

Summary: Users would have to do this by manipulating the environment before.

Changelog: [Internal]

Differential Revision: D57067036

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D57067036

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D57067036

[facebook-github-bot]

This pull request has been merged in facebook/react-native@01cbb173aa3b09508ed13569f5a494bb5eb7221d.

[github-actions[bot]]

This pull request was successfully merged by @blakef in 01cbb173aa3b09508ed13569f5a494bb5eb7221d.

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