[llvm] [clang] [clang][FatLTO] Avoid UnifiedLTO until it can support WPD/CFI (PR #79061)

[Nikita Popov via cfe-commits]

nikic wrote:

There's a merge conflict (probably after https://github.com/llvm/llvm-project/pull/79041).

https://github.com/llvm/llvm-project/pull/79061