selftests: new very basic kernel selftests directory

Bring a new kernel selftests directory in tools/testing/selftests.  To
add a new selftest, create a subdirectory with the sources and a
makefile that creates a target named "run_test" then add the
subdirectory name to the TARGET var in tools/testing/selftests/Makefile
and tools/testing/selftests/run_tests script.

This can help centralizing and maintaining any useful selftest that
developers usually tend to let rust in peace on some random server.
Suggested-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

tools/testing/selftests/Makefile

+TARGETS =
+
+all:
+	for TARGET in $(TARGETS); do \
+		make -C $$TARGET; \
+	done;
+
+clean:
+	for TARGET in $(TARGETS); do \
+		make -C $$TARGET clean; \
+	done;

tools/testing/selftests/run_tests

+#!/bin/bash
+
+TARGETS=
+
+for TARGET in $TARGETS
+do
+	$TARGET/run_test
+done