[llvm] [BPF] report `Invalid usage of the XADD return value"` elegantly (PR #92742)

[via llvm-commits]

eddyz87 wrote:

> Actually if there are some errors generated, there are no binary files emitted at all. I suppose this will not affect end-users.

Yes, code generation stops if `diagnose` reports errors, I was curious if this change could lead to some incorrect machine code that leads to further error reports and it looks like it can't. So all should be good.

https://github.com/llvm/llvm-project/pull/92742