[llvm] [Orc][examples] Fix lljit-with-remote-debugging test failure (PR #74764)

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lhames wrote:

> > @RoboTux @weliveindetail I don't think that `argc_sub1_elf.ll` contains anything x86-64 specific -- what if we just removed the triple instead?
> 
> I tried but then it complains that there is no target "". Perhaps it's worth fixing orc to support an empty target.

I missed this earlier -- that's a good idea. `LLJIT` seems like the right place to handle this: `addIRModule` can check for an empty triple and replace it with the triple reported through the `ExecutionSession`.

https://github.com/llvm/llvm-project/pull/74764