[llvm] [IR] Add require-logical-module module flag (PR #193502)

[Nikita Popov via llvm-commits]

nikic wrote:

> Would it be better in the meantime to have a module flag, and once we have a clearer picture of how much we can constraint it, do a proper datalayout addition/design?

Yes, I think this is fine. A module flag is the least intrusive way to introduce this for now.

Should still be documented in LangRef though.

https://github.com/llvm/llvm-project/pull/193502