[clang] [clang] Catch missing format attributes (PR #70024)

[Aaron Puchert via cfe-commits]

https://github.com/aaronpuchert commented:

I assume this is meant to imitate the GCC warning of the same name, which I found pretty useful. Would be nice to have the same in Clang!

https://github.com/llvm/llvm-project/pull/70024