[clang] [Clang] Consider reachability for file-scope warnings on initializers (PR #163885)

[Justin Stitt via cfe-commits]

JustinStitt wrote:

Thanks for the approvals @zwuis and @kees. Planning to click the big green button next week. @cor3ntin Did I properly address your concerns from a few weeks ago? I never heard back. Thanks :)

https://github.com/llvm/llvm-project/pull/163885