[clang] [Clang] Add -Wtrivial-auto-var-init warning for unreachable variables (PR #178318)

[Justin Stitt via cfe-commits]

JustinStitt wrote:

@efriedma-quic 
> It looks like this warning is gone in gcc 16. As far as I can tell, they fixed it so it just works: if you jump past the initialization of a variable, it's initialized by the jump itself.

Oh nice, thanks for spotting this.

Should we drop this PR so I can open a new PR implementing this forced initialization scheme that GCC is now using? Perhaps we could first ship this warning for immediate visibility for users?

https://github.com/llvm/llvm-project/pull/178318