[llvm] lli: Record the host triple on triple-less modules (PR #216132)

[Lang Hames via llvm-commits]

lhames wrote:

> > How was this discovered?
> 
> Bot failures on #215796
> 
> > `lli` seems like the wrong place to fix this to me. If RuntimeLibraryInfo needs a triple for all code then `LLJIT` should either auto-add the triple (as here) or reject modules that don't have one (if we want to insist that the client specify the triple).
> 
> The problem is these sort of tests that default to the host triple, so unless you want to pick an arbitrary set of host triples to duplicate these need to set something

I'm not sure I follow this? `LLJIT` should auto-detect a triple for the host (I believe that `lli` already provides an argument to override this too). I'm suggesting that rather than having `lli` set the triple for no-triple modules, we have `lli` pass the module through unmodified and have `LLJIT` apply it's triple. Only because the latter fixes all clients, not just `lli`. 

https://github.com/llvm/llvm-project/pull/216132