[llvm] DWARF: Emit `DW_AT_artificial` on artificial globals (PR #93118)

[Josh Stone via llvm-commits]

cuviper wrote:

> DIFlags is getting pretty full (again) and I'd be reluctant to add Artificial to it just to support this case.

Hmm? `DIFlagArtificial` already exists -- the possible addition was that globals currently don't have flags at all.

https://github.com/llvm/llvm-project/pull/93118