Add clang::lifetimebound annotation to llvm::function_ref (llvm#115019)

This helps catch dangling llvm::function_ref references, see llvm#114950,
llvm#114949, llvm#114808, llvm#114789

Author: hokein

llvm/include/llvm/ADT/STLFunctionalExtras.h

@@ -16,6 +16,7 @@
 #define LLVM_ADT_STLFUNCTIONALEXTRAS_H
 
 #include "llvm/ADT/STLForwardCompat.h"
+#include "llvm/Support/Compiler.h"
 
 #include <cstdint>
 #include <type_traits>
@@ -52,7 +53,7 @@ class function_ref<Ret(Params...)> {
 
   template <typename Callable>
   function_ref(
-      Callable &&callable,
+      Callable &&callable LLVM_LIFETIME_BOUND,
       // This is not the copy-constructor.
       std::enable_if_t<!std::is_same<remove_cvref_t<Callable>,
                                      function_ref>::value> * = nullptr,