[clang] [CIR] Fix problem with phantom function arguments (PR #140322)

[Bruno Cardoso Lopes via cfe-commits]

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

LGTM. Is there an easy to add a test for this? I understand sometimes it's hard, but just double checking.

https://github.com/llvm/llvm-project/pull/140322