[clang] [Clang] Added check for unexpanded pack in attribute [[assume]] (PR #91893)

[Azmat Yusuf via cfe-commits]

azmat-y wrote:

It was a pleasure working on this. 

I have received two emails from llvm build bot regarding failed builds, though the commit shows  8 build fails. How to go about investigating the cause of failures? Can you give me some pointers regarding this. And do the failures means this patch will need to be reverted?

https://github.com/llvm/llvm-project/pull/91893