[clang] [Clang] Use ExtWarn for static local variable in extern inline function (fixes #39524) (PR #166332)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> ping

Thanks for the ping! There's still a competing PR that's open; the other author may have disappeared but you should still coordinate so that we're only reviewing one set of changes in this area.

https://github.com/llvm/llvm-project/pull/166332