[clang] [clang][Darwin] Remove legacy framework search path logic in the frontend (PR #120149)

[Ian Anderson via cfe-commits]

ian-twilightcoder wrote:

> The next release is a few days away from branching. Is this ready or does this still need more work?

I think we need to restore `-internal-iframework`. We might want to consider how it orders against the other flags as well.

https://github.com/llvm/llvm-project/pull/120149