[llvm] LTO: Stop overwriting the merged module's DataLayout (PR #223987)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> I'm not very familiar with that area. Why do such modules have to be in the same context? Is there a place to read up on that?

They don't yet exist but it's something we've aspired to do in the past. Basically it would be useful to have host CPU code and offload device code see some object definitions from each other. The alignments etc. need to match, but there's other bits in the datalayout that don't match (e.g., alloca addrspace)

https://github.com/llvm/llvm-project/pull/223987