[clang] [clang][Sema] Fix for enums overflowing (#24667) (PR #78742)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman commented:

Thank you for working on this! One thing I would like to see are some tests added to `clang/test/C/C2x/` (`n3029.c` and `n3030.c`) that tests the examples and changes from the original papers/final standard to demonstrate the features are complete. There are other tests in that directory that show the boilerplate for C feature testing.

Aside from testing and some nits, I think this is pretty close to ready.

https://github.com/llvm/llvm-project/pull/78742