Update xcconfig in the main target only if using cocoapods

[GMinucci]

What does this PR do

Detects if user is using Cocoapods and, in that case, only set the xcconfig to the main build configurations to not break the Cocoapods' generate xcconfig file.

How can it be tested

The variants' commands should work in a project with or without Cocoapods. It should be tested in samples on both cases.

Task

Checklist:

• I ran make validation locally with success
• I have not introduced new bugs
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new errors

[github-actions]

	Warnings
⚠️	The library files were changed, but the tests remained unmodified. Consider updating or adding to the tests to match the library changes.

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