[clang] [clang][ARM] Fix warning for using VFP from interrupts. (PR #91870)

[David Spickett via cfe-commits]

================
@@ -492,6 +495,13 @@ Modified Compiler Flags
   now include dianostics about C++26 features that are not present in older
   versions.
 
+- Removed the "arm interrupt calling convention" warning that was included in
+  ``-Wextra`` without its own flag. This warning suggested adding
+  ``__attribute__((interrupt))`` to functions that are called from interrupt
+  handlers to prevent clobbering VFP registers. Following this suggestion leads
+  to unpredictable behavior by causing multiple exception returns from one
+  exception. Fixes #GH34876.
+
----------------
DavidSpickett wrote:

Note to other reviewers: This is in the modified flags section because -wextra itself is being modified. A part of it was removed but that part was never a separate flag so this doesn't need to go in the "removed compiler flags" section.

https://github.com/llvm/llvm-project/pull/91870