[clang] [sanitizer] [clang] Introduce fsanitize-bounds-strict-flex-arrays (PR #126163)

[Florian Mayer via cfe-commits]

================
@@ -444,6 +444,19 @@ class LangOptionsBase {
     IncompleteOnly = 3,
   };
 
+  enum class ArrayBoundsStrictFlexArraysLevelKind {
----------------
fmayer wrote:

we can't use -1 because it's a bitfield, but I can use 4

https://github.com/llvm/llvm-project/pull/126163