Makefile: Add run-test.mk to clean

Makefile

@@ -1053,6 +1053,7 @@ clean:
 	rm -rf vloghtb/Makefile vloghtb/refdat vloghtb/rtl vloghtb/scripts vloghtb/spec vloghtb/check_yosys vloghtb/vloghammer_tb.tar.bz2 vloghtb/temp vloghtb/log_test_*
 	rm -f tests/svinterfaces/*.log_stdout tests/svinterfaces/*.log_stderr tests/svinterfaces/dut_result.txt tests/svinterfaces/reference_result.txt tests/svinterfaces/a.out tests/svinterfaces/*_syn.v tests/svinterfaces/*.diff
 	rm -f  tests/tools/cmp_tbdata
+	rm -f $(addsuffix /run-test.mk,$(MK_TEST_DIRS))
 	-$(MAKE) -C docs clean
 	-$(MAKE) -C docs/images clean
 	rm -rf docs/source/cmd docs/util/__pycache__