torture: Use gawk instead of awk for systime() function

In many environments, gawk provides systime(), but awk doesn't.
This commit therefore changes awk scripts using systime() to instead be
gawk scripts.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/testing/selftests/rcutorture/bin/jitter.sh

@@ -23,12 +23,12 @@ spinmax=${4-1000}
 
 n=1
 
-starttime=`awk 'BEGIN { print systime(); }' < /dev/null`
+starttime=`gawk 'BEGIN { print systime(); }' < /dev/null`
 
 while :
 do
 	# Check for done.
-	t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
+	t=`gawk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
 	if test "$t" -gt "$duration"
 	then
 		exit 0;

tools/testing/selftests/rcutorture/bin/kvm-test-1-run.sh

@@ -123,7 +123,7 @@ qemu_args=$5
 boot_args=$6
 
 cd $KVM
-kstarttime=`awk 'BEGIN { print systime() }' < /dev/null`
+kstarttime=`gawk 'BEGIN { print systime() }' < /dev/null`
 if test -z "$TORTURE_BUILDONLY"
 then
 	echo ' ---' `date`: Starting kernel
@@ -177,7 +177,7 @@ do
 	then
 		qemu_pid=`cat "$resdir/qemu_pid"`
 	fi
-	kruntime=`awk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
+	kruntime=`gawk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
 	if test -z "$qemu_pid" || kill -0 "$qemu_pid" > /dev/null 2>&1
 	then
 		if test $kruntime -ge $seconds
@@ -213,7 +213,7 @@ then
 	oldline="`tail $resdir/console.log`"
 	while :
 	do
-		kruntime=`awk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
+		kruntime=`gawk 'BEGIN { print systime() - '"$kstarttime"' }' < /dev/null`
 		if kill -0 $qemu_pid > /dev/null 2>&1
 		then
 			: