[clang] [clang][Sema] Emit warnings about incorrect AVR interrupt/signal handlers (PR #125997)

[Jianjian Guan via cfe-commits]

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@@ -351,8 +351,8 @@ def warn_arm_interrupt_vfp_clobber : Warning<
 def err_arm_interrupt_called : Error<
   "interrupt service routine cannot be called directly">;
 def warn_interrupt_attribute_invalid : Warning<
-   "%select{MIPS|MSP430|RISC-V}0 'interrupt' attribute only applies to "
-   "functions that have %select{no parameters|a 'void' return type}1">,
+   "%select{MIPS|MSP430|RISC-V|AVR}0 '%1' attribute only applies to "
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jacquesguan wrote:

If only support `interrupt` and `signal`, I think we should use the `select{}` format.

https://github.com/llvm/llvm-project/pull/125997