rcutorture: Provide rudimentary Makefile

This commit provides a rudimentary Makefile that runs a 10-minute
rcutorture test on scenario TREE01.  This must be run on a system capable
of spawning virtual machines and with everything installed to permit
building Linux kernels.
Reported-by: Shuah Khan <shuah@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

tools/testing/selftests/rcutorture/Makefile

+# SPDX-License-Identifier: GPL-2.0+
+all:
+	( cd ../../../..; tools/testing/selftests/rcutorture/bin/kvm.sh --duration 10 --configs TREE01 )