Move BuildConfiguration to BuildSettingsKit

[kean]

Changes:

• Move BuildConfiguration (used across multiple targets) to BuildSettingsKit
• Instead of using separate compiler flag, define build configuration in .plist (.xcconfig)
• Remove ~= operator – we have only three types and it's rarely used
• Rename .localDeveloper to .debug to match the actual build configurations in Xcode

To test:

When using Debug build configuration:

(lldb) po BuildConfiguration.current
BuildSettingsKit.BuildConfiguration.debug

Release:

(lldb) po BuildConfiguration.current
BuildSettingsKit.BuildConfiguration.release

Regression Notes

1. Potential unintended areas of impact

2. What I did to test those areas of impact (or what existing automated tests I relied on)

3. What automated tests I added (or what prevented me from doing so)

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing checklist:

• WordPress.com sites and self-hosted Jetpack sites.
• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)

[dangermattic]

	1 Warning
⚠️	This PR is assigned to the milestone 25.9. The due date for this milestone has already passed. Please assign it to a milestone with a later deadline or check whether the release for this milestone has already been finished.

Generated by 🚫 Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr24276-6d9c36e
	Version	25.8
	Bundle ID	org.wordpress.alpha
	Commit	6d9c36e
	App Center Build	WPiOS - One-Offs #11774

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr24276-6d9c36e
	Version	25.8
	Bundle ID	com.jetpack.alpha
	Commit	6d9c36e
	App Center Build	jetpack-installable-builds #10800

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[kean]

I'm planning to remove this duplication (WP/JP), but it requires refactoring the .xcconfig file. There has two be only three:

Common <- WordPress
Common  <- Jetpack