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

[Fangrui Song via cfe-commits]

================
@@ -330,6 +330,14 @@ def warn_alias_with_section : Warning<
   "as the %select{aliasee|resolver}2">,
   InGroup<IgnoredAttributes>;
 
+let CategoryName = "Bounds Safety Issue" in {
+def err_bounds_safety_lang_not_supported : Error<
+  "bounds safety is only supported for C">;
+def warn_bounds_safety_asm_ignored : Warning<
+  "'-fbounds-safety' is ignored for assembly">,
----------------
MaskRay wrote:

Conventionally the language compatibility checking and other checking is performed in Driver, not in Frontend.. If you move the language check to Driver, the diagnostic will be natural since clang integrated assembler uses `ClangAs` instead of `Clang`.

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