/claim #6456 Resolves https://github.com/tuist/tuist/issues/6456

Short description 📝

As mentioned in the issue this PR seeks to solve, previously the internal target resource generation was removed because it would override GCC_PREFIX_HEADER as set by the user.

This seeks to fix this by using .combine to use not override the user option, and restores internal target resource generation.

How to test the changes locally 🧐

Internal targets should have tuist resource accessors.

Contributor checklist ✅

• The code has been linted using run mise run lint-fix
• The change is tested via unit testing or acceptance testing, or both
• The title of the PR is formulated in a way that is usable as a changelog entry
• In case the PR introduces changes that affect users, the documentation has been updated

Reviewer checklist ✅

• The code architecture and patterns are consistent with the rest of the codebase
• Reviewer has checked that, if needed, the PR includes the label changelog:added, changelog:fixed, or changelog:changed, and the title is usable as a changelog entry