objtool: Remove libsubcmd.a when make clean

The file libsubcmd.a still exists after make clean, remove it.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/1652258270-6278-3-git-send-email-yangtiezhu@loongson.cn

tools/objtool/Makefile

@@ -63,7 +63,7 @@ $(LIBSUBCMD): fixdep FORCE
 clean:
 	$(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL)
 	$(Q)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
-	$(Q)$(RM) $(OUTPUT)arch/x86/lib/inat-tables.c $(OUTPUT)fixdep
+	$(Q)$(RM) $(OUTPUT)arch/x86/lib/inat-tables.c $(OUTPUT)fixdep $(LIBSUBCMD)
 
 FORCE: