Makefile: add smoke test with gc=leaking to test dead asm code

Makefile

@@ -451,6 +451,9 @@ endif
 	@$(MD5SUM) test.nro
 	$(TINYGO) build -size short -o test.hex -target=pca10040 -opt=0     ./testdata/stdlib.go
 	@$(MD5SUM) test.hex
+ifneq ($(OS),Windows_NT)
+	$(TINYGO) build -o test.elf -gc=leaking -scheduler=none examples/serial
+endif
 
 
 wasmtest: