Add support for recording named runtime with rr

The traces of the named process are stored in the directory
$system_test/nsX/named-Y/.

bin/tests/system/README.md

@@ -114,6 +114,13 @@ Alternately, using the make command is also supported:
 
     make [-j numproc] test
 
+### rr
+
+When running system tests, named can be run under the rr tool. rr records a
+trace to the $system_test/nsX/named-Y/ directory, which can be later used to
+replay named. To enable this, execute start.pl with the USE_RR environment
+variable set.
+
 ### Test Artifacts
 
 Each test module is executed inside a unique temporary directory which contains

bin/tests/system/start.pl

@@ -232,6 +232,9 @@ sub construct_ns_command {
 
 	if ($taskset) {
 		$command = "taskset $taskset $NAMED ";
+	} elsif ($ENV{'USE_RR'}) {
+		$ENV{'_RR_TRACE_DIR'} = ".";
+		$command = "rr record --chaos $NAMED ";
 	} else {
 		$command = "$NAMED ";
 	}