Just a quick note which may or may not solve your React Native project's problem.

I was seeing this error when trying to run or build my project on iOS.

The following build commands failed:
        PhaseScriptExecution [CP-User] Generate Specs
...Pods.build/Debug-iphonesimulator/React-rncore.build/Script-F00BA4.sh...(in target 'React-rncore' from project 'Pods')

Clues:

• the error comes from a shell script in rncore, from project Pods, during "PhaseScriptExecution"

Investigation:

• deleted Pods folder and Podfile.lock, reinstalled pods
• checked the Podfile and the use_react_native configuration, looked okay
• hmm PhaseScriptExecution seems interesting, I remember setting up something in XCode for my Target's Build Phases

There!

• the rncore script throwing the error must be getting called by react-native-xcode.sh -- But what's setting node binary?
• open up .xcode.env.local -- it set it to some weird temporary directory, let's fix that
• npx react-native run-ios
• FIXED!

No hate please, this is a note-to-self that I'm making public in the hopes that it helps any devs that encounter something similar.