The .xcode.env file exists to make it easy for developers to tell Xcode where to find the node executable on their system. This file is intended to be checked in to source control, and it is a generic mechanism that works on most machines. If you're in your team and you all have the same setup which is non-standard, you may want to modify this file.
The .xcode.env.local file exists to allow you to override the behavior of .xcode.env on your system. It is not intended to be checked in to source control. When running a build, if you have accidentally included it in your project then EAS Build will remove the file and warn you. If you use .easignore then you should add .xcode.env.local to it. You also likely want it to be included in your .gitignore, so your local configuration is not shared with colleagues. Note that .xcode.env.local is automatically generated by pod install.