[llvm] [VPlan] Enable DebugLoc coverage tracking (PR #156045)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks!

> Unfortunately not - by design, this is NFC unless the DebugLoc coverage tracking CMake flag is turned on, and even when it is enabled there is no IR representation for annotated locations currently - the only visible output from this change will be in Debugify's bug reporting (as run on the [buildbot](https://lab.llvm.org/staging/#/builders/222)).

Ah I see, so there's no option to enable it just for opt.

https://github.com/llvm/llvm-project/pull/156045