interpret/miri: call panic_cannot_unwind lang item instead of hard-coding the same message

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -223,6 +223,9 @@ pub trait Machine<'mir, 'tcx: 'mir>: Sized {
         throw_unsup_format!("aborting execution is not supported")
     }
 
+    /// Called when unwinding reached a state where execution should be terminated.
+    fn unwind_terminate(_ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx>;
+
     /// Called for all binary operations where the LHS has pointer type.
     ///
     /// Returns a (value, overflowed) pair if the operation succeeded
@@ -499,6 +502,11 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
         false
     }
 
+    #[inline(always)]
+    fn unwind_terminate(_ecx: &mut InterpCx<$mir, $tcx, Self>) -> InterpResult<$tcx> {
+        unreachable!("unwinding cannot happen during compile-time evaluation")
+    }
+
     #[inline(always)]
     fn call_extra_fn(
         _ecx: &mut InterpCx<$mir, $tcx, Self>,