tests/thread_flags_xtimer: migrate to testrunner script

tests/thread_flags_xtimer/Makefile

@@ -5,3 +5,6 @@ USEMODULE += core_thread_flags
 USEMODULE += xtimer
 
 include $(RIOTBASE)/Makefile.include
+
+test:
+	tests/01-run.py

tests/thread_flags_xtimer/tests/01-run.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+
+sys.path.append(os.path.join(os.environ['RIOTBASE'], 'dist/tools/testrunner'))
+import testrunner
+
+
+def testfunc(child):
+    child.expect("START")
+    for i in range(5):
+        child.expect_exact("+++ timeout  {} +++".format(i + 1))
+    child.expect("SUCCESS")
+
+
+if __name__ == "__main__":
+    sys.exit(testrunner.run(testfunc))