[exp] Dump PERF_EVENTS variables

bin/mc-2/exp

@@ -148,6 +148,8 @@ dump_args() {
     echo "USE_PERF    = $use_perfs"   >>$args_file
     echo "AUTOGROUP   = $autogroups"  >>$args_file
     echo "REPEAT      = $repeat"      >>$args_file
+    echo
+    echo "PERF_EVENTS = $PERF_EVENTS" >>$args_file
 }
 
 dump_programs() {