[clang] [clang][modules] Determine if the SDK supports builtin modules independent of the target (PR #134005)

[Cyndy Ishida via cfe-commits]

https://github.com/cyndyishida approved this pull request.

LGTM. I was a bit worried about the fallout that other target triples using the same sdks would now opt into this behavior but if that were the case they'd already be running into modularization errors (e.g. `found_incompatible_headers__check_search_paths`)

https://github.com/llvm/llvm-project/pull/134005