Run build script phase only when needed

[nilo-ms]

Proposed changes

Run build script phase only when needed. This PR solve the following warning:

I'm using this as a reference:
https://developer.apple.com/documentation/Xcode/improving-the-speed-of-incremental-builds#Declare-inputs-and-outputs-for-custom-scripts-and-build-rules

Type of change

• Feature work
• Bug fix
• Documentation
• Engineering change
• Test
• Logging/Telemetry

Risk

• High – Errors could cause MAJOR regression of many scenarios. (Example: new large features or high level infrastructure changes)
• Medium – Errors could cause regression of 1 or more scenarios. (Example: somewhat complex bug fixes, small new features)
• Small – No issues are expected. (Example: Very small bug fixes, string changes, or configuration settings changes)