Add LD_RUNPATH_SEARCH_PATHS to extensionkit-extension preset

[alessionossa]

Add LD_RUNPATH_SEARCH_PATHS option as it is for other types of extensions (e.g. app extension).
I followed the same logic of #272, copying the value from the current version of SettingPresets/Products/app-extension.yml

[freddi-kit]

I started thinking it also should be fixed by XcodeProj (yes, this pr also should be okay), could you check it if you have time?

https://github.com/tuist/XcodeProj/blob/b6de1bfe021b861c94e7c83821b595083f74b997/Sources/XcodeProj/Utils/BuildSettingsProvider.swift#L224-L229

[alessionossa]

I started thinking it also should be fixed by XcodeProj (yes, this pr also should be okay), could you check it if you have time?

https://github.com/tuist/XcodeProj/blob/b6de1bfe021b861c94e7c83821b595083f74b997/Sources/XcodeProj/Utils/BuildSettingsProvider.swift#L224-L229

@freddi-kit I see that targetSettings(platform:, product:) is only called by targetDefault(variant:, platform:, product:, swift:) and we are not calling the latter method anywhere. Are you think of using that instead of "custom overrides"?

[yonaskolb]

Thanks @alessionossa. Could you add a changelog entry as well please.

And at the moment we aren't using the BuildSettingsProvider from XcodeProj, as that didn't exist at the time. I've created a new issue to track that here #1267