force make to run tests single threaded by adding fake dependencies to all other test targets

makefile

@@ -112,7 +112,7 @@ cppcheck:
 	cppcheck-htmlreport --file=output/cppcheck/cppcheck.xml --title="Shellmatta" --report-dir=output/cppcheck/html
 
 
-$(TEST_RUN_TARGETS): $(TEST_TARGETS)
+$(TEST_RUN_TARGETS): $(TEST_TARGETS) $(filter-out $@,$(TEST_RUN_TARGETS))
 	- @mkdir -p output/test/$@/report
 	@echo running test $@:
 #	remove coverage from former run