selftests: Add futex tests to the top-level Makefile

Enable futex tests to be built and run with the make kselftest and
associated targets.

Most of the tests require escalated privileges. These return ERROR, and
run.sh continues.

Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: linux-api@vger.kernel.org
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/Makefile

@@ -4,6 +4,7 @@ TARGETS += efivarfs
 TARGETS += exec
 TARGETS += firmware
 TARGETS += ftrace
+TARGETS += futex
 TARGETS += kcmp
 TARGETS += memfd
 TARGETS += memory-hotplug