perf metrics: Fix SEGV with --for-each-cgroup

Ensure the metric threshold is copied correctly or else a use of
uninitialized memory happens.

Fixes: d0a3052 ("perf metric: Compute and print threshold values")
Reported-by: Namhyung Kim <[email protected]>
Signed-off-by: Ian Rogers <[email protected]>
Tested-by: Namhyung Kim <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kajol Jain <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: captain5050

tools/perf/util/metricgroup.c

@@ -1730,6 +1730,7 @@ int metricgroup__copy_metric_events(struct evlist *evlist, struct cgroup *cgrp,
 				return -ENOMEM;
 
 			new_expr->metric_expr = old_expr->metric_expr;
+			new_expr->metric_threshold = old_expr->metric_threshold;
 			new_expr->metric_name = strdup(old_expr->metric_name);
 			if (!new_expr->metric_name)
 				return -ENOMEM;