build: scan.mk: remove not used variable SCAN_STAMP

It was left behind since rewrite of metadata scanning done with commit
bdc9419 in July 2007

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

include/scan.mk

@@ -28,7 +28,7 @@ endef
 
 define PackageDir
   $(TMP_DIR)/.$(SCAN_TARGET): $(TMP_DIR)/info/.$(SCAN_TARGET)-$(1)
-  $(TMP_DIR)/info/.$(SCAN_TARGET)-$(1): $(SCAN_DIR)/$(2)/Makefile $(SCAN_STAMP) $(foreach DEP,$(DEPS_$(SCAN_DIR)/$(2)/Makefile) $(SCAN_DEPS),$(wildcard $(if $(filter /%,$(DEP)),$(DEP),$(SCAN_DIR)/$(2)/$(DEP))))
+  $(TMP_DIR)/info/.$(SCAN_TARGET)-$(1): $(SCAN_DIR)/$(2)/Makefile $(foreach DEP,$(DEPS_$(SCAN_DIR)/$(2)/Makefile) $(SCAN_DEPS),$(wildcard $(if $(filter /%,$(DEP)),$(DEP),$(SCAN_DIR)/$(2)/$(DEP))))
 	{ \
 		$$(call progress,Collecting $(SCAN_NAME) info: $(SCAN_DIR)/$(2)) \
 		echo Source-Makefile: $(SCAN_DIR)/$(2)/Makefile; \
@@ -93,7 +93,7 @@ $(TARGET_STAMP)::
 		} \
 	)
 
-$(TMP_DIR)/.$(SCAN_TARGET): $(TARGET_STAMP) $(SCAN_STAMP)
+$(TMP_DIR)/.$(SCAN_TARGET): $(TARGET_STAMP)
 	$(call progress,Collecting $(SCAN_NAME) info: merging...)
 	-cat $(FILELIST) | awk '{gsub(/\//, "_", $$0);print "$(TMP_DIR)/info/.$(SCAN_TARGET)-" $$0}' | xargs cat > $@ 2>/dev/null
 	$(call progress,Collecting $(SCAN_NAME) info: done)