make: Fix object clean-up

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/programs/Makefile b/programs/Makefile
index 1f2d719..80368d4 100644
--- a/programs/Makefile
+++ b/programs/Makefile
@@ -417,6 +417,7 @@
 clean:
 ifndef WINDOWS
 	rm -f $(EXES)
+	rm -f */*.o
 	-rm -f ssl/ssl_pthread_server$(EXEXT)
 	-rm -f test/cpp_dummy_build.cpp test/cpp_dummy_build$(EXEXT)
 	-rm -f test/dlopen$(EXEXT)