message: also prune caller_location frames when backtrace=off
diff: @@ -96,6 +96,9 @@ fn prune_stacktrace<'mir, 'tcx>(
  ) -> (Vec<FrameInfo<'tcx>>, bool) {
  match ecx.machine.backtrace_style {
  BacktraceStyle::Off => {
  + // Remove all frames marked with `caller_location` -- that attribute indicates we
  + // usually want to point at the caller, not them.
  + stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(*ecx.tcx));
  // Retain one frame so that we can print a span for the error itself
  stacktrace.truncate(1);
  (stacktrace, false)
  