[llvm] Fix silent truncation of inline ASM `srcloc` cookie when going through a `DiagnosticInfoSrcMgr` (PR #84559)

[Simon Tatham via llvm-commits]

https://github.com/statham-arm commented:

Thanks – good catch!

But I notice that just below the declaration of `DiagnosticInfoSrcMgr` is another class `DiagnosticInfoDontCall`, which also has an `unsigned LocCookie`. Should that one be widened too?

https://github.com/llvm/llvm-project/pull/84559