lib/tests: use the "check_" prefix for tests

The "check_" prefix ensures the test programs are not installed and are
only built when "make check" is run.

Signed-off-by: Thomas Wood <thomas.wood@intel.com>

lib/tests/Makefile.sources

@@ -1,8 +1,4 @@
-noinst_PROGRAMS = \
-	$(TESTS_testsuite) \
-	$(NULL)
-
-TESTS_testsuite = \
+check_PROGRAMS = \
 	igt_no_exit \
 	igt_no_exit_list_only \
 	igt_fork_helper \
@@ -11,13 +7,13 @@ TESTS_testsuite = \
 	igt_simulation \
 	$(NULL)
 
-TESTS_testsuite_scripts = \
+check_SCRIPTS = \
 	igt_command_line.sh \
 	$(NULL)
 
 TESTS = \
-	$(TESTS_testsuite) \
-	$(TESTS_testsuite_scripts) \
+	$(check_PROGRAMS) \
+	$(check_SCRIPTS) \
 	$(NULL)
 
 # Test that exercise specific asserts in the test framework library and are