tools/resolve_btfids: Check objects before removing

We want this clean to be called from tree's root clean
and that one is silent if there's nothing to clean.

Adding check for all object to clean and display CLEAN
messages only if there are objects to remove.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210205124020.683286-3-jolsa@kernel.org
diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
index 1d46a24..be09ec4 100644
--- a/tools/bpf/resolve_btfids/Makefile
+++ b/tools/bpf/resolve_btfids/Makefile
@@ -64,13 +64,20 @@
 	$(call msg,LINK,$@)
 	$(Q)$(CC) $(BINARY_IN) $(LDFLAGS) -o $@ $(BPFOBJ) $(SUBCMDOBJ) $(LIBS)
 
+clean_objects := $(wildcard $(OUTPUT)/*.o                \
+                            $(OUTPUT)/.*.o.cmd           \
+                            $(OUTPUT)/.*.o.d             \
+                            $(OUTPUT)/libbpf             \
+                            $(OUTPUT)/libsubcmd          \
+                            $(OUTPUT)/resolve_btfids)
+
+ifneq ($(clean_objects),)
 clean: fixdep-clean
 	$(call msg,CLEAN,$(BINARY))
-	$(Q)$(RM) -f $(BINARY); \
-	$(RM) -rf $(if $(OUTPUT),$(OUTPUT),.)/feature; \
-	$(RM) -rf $(OUTPUT)/libbpf; \
-	$(RM) -rf $(OUTPUT)/libsubcmd; \
-	find $(if $(OUTPUT),$(OUTPUT),.) -name \*.o -or -name \*.o.cmd -or -name \*.o.d | xargs $(RM)
+	$(Q)$(RM) -rf $(clean_objects)
+else
+clean:
+endif
 
 tags:
 	$(call msg,GEN,,tags)