[clang] [Driver][BoundsSafety] Add -fbounds-safety-experimental flag (PR #70480)

[Fangrui Song via cfe-commits]

================
@@ -1412,6 +1412,9 @@ def FunctionMultiVersioning
 
 def NoDeref : DiagGroup<"noderef">;
 
+// Bounds safety specific warnings
+def IgnoredBoundsSafety : DiagGroup<"ignored-bounds-safety">;
----------------
MaskRay wrote:

This is `-Wignored-bounds-safety` is not used.

https://github.com/llvm/llvm-project/pull/70480