[clang] [clang][driver] Expose a frontend option for trap-unreachable (PR #174894)

[Paul Kirth via cfe-commits]

ilovepi wrote:

> How does this interact with LTO?

Thanks for pointing that out. I've added options to make sure the right backend options get passed to the linker. Ideally, we wouldn't be relying on target options, but for now its no worse than other options. Hopefully we can get a better mechanism for tracking these types of options in the IR.

https://github.com/llvm/llvm-project/pull/174894