[clang] [clang] Extend -Wunused-but-set-variable to static globals (PR #178342)

[Devon Loehr via cfe-commits]

DKLoehr wrote:

Thanks for contributing to LLVM! We've started to see the warning fire a lot more in chromium builds due to the extended coverage. Can we move the new functionality behind a separate flag (e.g. `-Wunused-but-set-global` or similar) so that we can suppress just the new instances of the warning without losing coverage for non-globals? That sort of separate flag helps a lot with migrations as we investigate and fix our issues.

https://github.com/llvm/llvm-project/pull/178342