[clang] [RFC][Clang] Enable custom type checking for printf (PR #86801)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

I'm not keen on reimplementing the checking logic manually; I worry this is going to be a slippery slope where we start with `printf` today, but then need to do the same thing for the rest of the family at some point in the future.

Would it make sense for us to define a `LibBuiltin` specific to OpenCL languages to expose a different signature for OpenCL? And change `BuiltinPrintf` from `Builtin` to `LangBuiltin` to do similar for the builtin form?

https://github.com/llvm/llvm-project/pull/86801