[clang] [Clang][CodeGen] Emit “trap reasons” on UBSan traps (PR #145967)

[Dan Liew via cfe-commits]

delcypher wrote:

@fmayer

> I would prefer this to be behind a flag (not necessarily in this PR), even if it's default turned on. People might not want synthetic frames added to their debug information and the top frame to point to the real code; also as this somewhat overlaps with the logic of `-fsanitize-annotate-debug-info`, with a flag people can choose which one they want.

Do you have a concrete use case where it would be problematic to emit the trap reasons in debug info as the patch does? We are not opposed to adding a flag that allows it to be disabled (e.g. `-fno-sanitize-annotated-traps` or something similar) provided the trap reasons are emitted by default. That being said we don't want to implement things that won't be used. What use case(s) do you have in mind?

https://github.com/llvm/llvm-project/pull/145967